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	$236.38	7.212%	$253.4277	$253.43	$253.45	$253.40
Purchase #2	$33.86	8.295%	$36.6687	$36.67	$36.65	$36.70
Purchase #3	$242.72	13.443%	$275.3488	$275.35	$275.35	$275.30
Purchase #4	$236.49	11.651%	$264.0434	$264.04	$264.05	$264.00
Purchase #5	$126.95	3.455%	$131.3361	$131.34	$131.35	$131.30
Purchase #6	$104.33	8.568%	$113.269	$113.27	$113.25	$113.30
Purchase #7	$61.99	8.538%	$67.2827	$67.28	$67.30	$67.30
7 purchase totals =	$1,042.72		$1,141.3764	$1,141.38	$1,141.40	$1,141.30