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	$200.72	7.570%	$215.9145	$215.91	$215.90	$215.90
Purchase #2	$165.58	3.846%	$171.9482	$171.95	$171.95	$171.90
Purchase #3	$78.28	10.585%	$86.5659	$86.57	$86.55	$86.60
Purchase #4	$34.65	6.779%	$36.9989	$37.00	$37.00	$37.00
Purchase #5	$210.33	9.180%	$229.6383	$229.64	$229.65	$229.60
Purchase #6	$52.75	8.868%	$57.4279	$57.43	$57.45	$57.40
Purchase #7	$53.42	11.216%	$59.4116	$59.41	$59.40	$59.40
7 purchase totals =	$795.73		$857.9053	$857.91	$857.90	$857.80