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	$50.91	8.846%	$55.4135	$55.41	$55.40	$55.40
Purchase #2	$148.94	10.446%	$164.4983	$164.50	$164.50	$164.50
Purchase #3	$209.59	9.303%	$229.0882	$229.09	$229.10	$229.10
Purchase #4	$133.30	12.268%	$149.6532	$149.65	$149.65	$149.70
Purchase #5	$25.90	12.166%	$29.051	$29.05	$29.05	$29.10
Purchase #6	$169.70	12.305%	$190.5816	$190.58	$190.60	$190.60
Purchase #7	$228.56	6.287%	$242.9296	$242.93	$242.95	$242.90
7 purchase totals =	$966.90		$1,061.2154	$1,061.21	$1,061.25	$1,061.30