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	$210.39	5.124%	$221.1704	$221.17	$221.15	$221.20
Purchase #2	$198.63	12.627%	$223.711	$223.71	$223.70	$223.70
Purchase #3	$29.45	12.532%	$33.1407	$33.14	$33.15	$33.10
Purchase #4	$110.72	7.641%	$119.1801	$119.18	$119.20	$119.20
Purchase #5	$199.32	5.333%	$209.9497	$209.95	$209.95	$209.90
Purchase #6	$160.78	13.418%	$182.3535	$182.35	$182.35	$182.40
Purchase #7	$20.35	10.593%	$22.5057	$22.51	$22.50	$22.50
7 purchase totals =	$929.64		$1,012.0111	$1,012.01	$1,012.00	$1,012.00