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	$232.78	10.453%	$257.1125	$257.11	$257.10	$257.10
Purchase #2	$83.47	5.553%	$88.1051	$88.11	$88.10	$88.10
Purchase #3	$211.57	5.511%	$223.2296	$223.23	$223.25	$223.20
Purchase #4	$184.46	3.796%	$191.4621	$191.46	$191.45	$191.50
Purchase #5	$197.84	12.668%	$222.9024	$222.90	$222.90	$222.90
Purchase #6	$85.64	12.279%	$96.1557	$96.16	$96.15	$96.20
Purchase #7	$128.58	4.617%	$134.5165	$134.52	$134.50	$134.50
7 purchase totals =	$1,124.34		$1,213.4839	$1,213.49	$1,213.45	$1,213.50