Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$213.92	10.325%	$236.0072	$236.01	$236.00	$236.00
Purchase #2	$120.57	5.608%	$127.3316	$127.33	$127.35	$127.30
Purchase #3	$100.59	11.235%	$111.8913	$111.89	$111.90	$111.90
Purchase #4	$232.83	7.533%	$250.3691	$250.37	$250.35	$250.40
Purchase #5	$215.46	9.645%	$236.2411	$236.24	$236.25	$236.20
Purchase #6	$201.40	4.487%	$210.4368	$210.44	$210.45	$210.40
Purchase #7	$104.39	11.358%	$116.2466	$116.25	$116.25	$116.20
7 purchase totals =	$1,189.16		$1,288.5237	$1,288.53	$1,288.55	$1,288.40