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	$198.94	11.473%	$221.7644	$221.76	$221.75	$221.80
Purchase #2	$40.36	6.333%	$42.916	$42.92	$42.90	$42.90
Purchase #3	$150.59	9.721%	$165.2289	$165.23	$165.25	$165.20
Purchase #4	$189.30	10.809%	$209.7614	$209.76	$209.75	$209.80
Purchase #5	$114.82	4.361%	$119.8273	$119.83	$119.85	$119.80
Purchase #6	$62.34	6.491%	$66.3865	$66.39	$66.40	$66.40
Purchase #7	$234.32	11.149%	$260.4443	$260.44	$260.45	$260.40
7 purchase totals =	$990.67		$1,086.3288	$1,086.33	$1,086.35	$1,086.30