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	$86.56	3.656%	$89.7246	$89.72	$89.70	$89.70
Purchase #2	$204.95	8.335%	$222.0326	$222.03	$222.05	$222.00
Purchase #3	$106.98	6.329%	$113.7508	$113.75	$113.75	$113.80
Purchase #4	$94.86	8.678%	$103.092	$103.09	$103.10	$103.10
Purchase #5	$56.65	3.852%	$58.8322	$58.83	$58.85	$58.80
Purchase #6	$210.89	5.527%	$222.5459	$222.55	$222.55	$222.50
Purchase #7	$209.29	13.315%	$237.157	$237.16	$237.15	$237.20
7 purchase totals =	$970.18		$1,047.1351	$1,047.13	$1,047.15	$1,047.10