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	$44.40	8.840%	$48.325	$48.33	$48.35	$48.30
Purchase #2	$77.75	4.349%	$81.1313	$81.13	$81.15	$81.10
Purchase #3	$58.61	12.494%	$65.9327	$65.93	$65.95	$65.90
Purchase #4	$205.51	11.356%	$228.8477	$228.85	$228.85	$228.80
Purchase #5	$106.69	4.717%	$111.7226	$111.72	$111.70	$111.70
Purchase #6	$202.87	11.148%	$225.4859	$225.49	$225.50	$225.50
Purchase #7	$169.91	12.344%	$190.8837	$190.88	$190.90	$190.90
7 purchase totals =	$865.74		$952.3289	$952.33	$952.40	$952.20