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	$244.66	8.117%	$264.5191	$264.52	$264.50	$264.50
Purchase #2	$237.96	13.145%	$269.2398	$269.24	$269.25	$269.20
Purchase #3	$34.43	13.769%	$39.1707	$39.17	$39.15	$39.20
Purchase #4	$234.98	3.548%	$243.3171	$243.32	$243.30	$243.30
Purchase #5	$239.73	13.308%	$271.6333	$271.63	$271.65	$271.60
Purchase #6	$6.94	12.625%	$7.8162	$7.82	$7.80	$7.80
Purchase #7	$71.49	10.185%	$78.7713	$78.77	$78.75	$78.80
7 purchase totals =	$1,070.19		$1,174.4675	$1,174.47	$1,174.40	$1,174.40