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	$96.54	5.709%	$102.0515	$102.05	$102.05	$102.10
Purchase #2	$221.51	5.587%	$233.8858	$233.89	$233.90	$233.90
Purchase #3	$123.76	4.501%	$129.3304	$129.33	$129.35	$129.30
Purchase #4	$122.47	3.393%	$126.6254	$126.63	$126.65	$126.60
Purchase #5	$233.60	7.119%	$250.23	$250.23	$250.25	$250.20
Purchase #6	$69.32	13.673%	$78.7981	$78.80	$78.80	$78.80
Purchase #7	$19.95	3.464%	$20.6411	$20.64	$20.65	$20.60
7 purchase totals =	$887.15		$941.5623	$941.57	$941.65	$941.50