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	$160.53	7.606%	$172.7399	$172.74	$172.75	$172.70
Purchase #2	$160.71	8.178%	$173.8529	$173.85	$173.85	$173.90
Purchase #3	$123.92	12.185%	$139.0197	$139.02	$139.00	$139.00
Purchase #4	$212.60	9.813%	$233.4624	$233.46	$233.45	$233.50
Purchase #5	$56.79	3.834%	$58.9673	$58.97	$58.95	$59.00
Purchase #6	$82.94	12.814%	$93.5679	$93.57	$93.55	$93.60
Purchase #7	$69.37	4.829%	$72.7199	$72.72	$72.70	$72.70
7 purchase totals =	$866.86		$944.3300	$944.33	$944.25	$944.40