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	$225.89	9.708%	$247.8194	$247.82	$247.80	$247.80
Purchase #2	$49.66	5.556%	$52.4191	$52.42	$52.40	$52.40
Purchase #3	$210.64	5.810%	$222.8782	$222.88	$222.90	$222.90
Purchase #4	$76.34	7.833%	$82.3197	$82.32	$82.30	$82.30
Purchase #5	$38.81	9.673%	$42.5641	$42.56	$42.55	$42.60
Purchase #6	$211.53	8.271%	$229.0256	$229.03	$229.05	$229.00
Purchase #7	$149.44	10.486%	$165.1103	$165.11	$165.10	$165.10
7 purchase totals =	$962.31		$1,042.1364	$1,042.14	$1,042.10	$1,042.10