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	$114.90	5.165%	$120.8346	$120.83	$120.85	$120.80
Purchase #2	$141.50	4.160%	$147.3864	$147.39	$147.40	$147.40
Purchase #3	$103.32	7.573%	$111.1444	$111.14	$111.15	$111.10
Purchase #4	$144.73	3.749%	$150.1559	$150.16	$150.15	$150.20
Purchase #5	$82.43	13.119%	$93.244	$93.24	$93.25	$93.20
Purchase #6	$116.66	10.562%	$128.9816	$128.98	$129.00	$129.00
Purchase #7	$211.80	11.335%	$235.8075	$235.81	$235.80	$235.80
7 purchase totals =	$915.34		$987.5544	$987.55	$987.60	$987.50