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	$106.41	5.480%	$112.2413	$112.24	$112.25	$112.20
Purchase #2	$210.94	3.345%	$217.9959	$218.00	$218.00	$218.00
Purchase #3	$104.40	6.194%	$110.8665	$110.87	$110.85	$110.90
Purchase #4	$244.25	12.333%	$274.3734	$274.37	$274.35	$274.40
Purchase #5	$155.38	11.274%	$172.8975	$172.90	$172.90	$172.90
Purchase #6	$156.62	9.326%	$171.2264	$171.23	$171.25	$171.20
Purchase #7	$20.65	5.394%	$21.7639	$21.76	$21.75	$21.80
7 purchase totals =	$998.65		$1,081.3649	$1,081.37	$1,081.35	$1,081.40