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	$20.33	11.207%	$22.6084	$22.61	$22.60	$22.60
Purchase #2	$179.65	9.269%	$196.3018	$196.30	$196.30	$196.30
Purchase #3	$239.45	3.364%	$247.5051	$247.51	$247.50	$247.50
Purchase #4	$53.36	6.364%	$56.7558	$56.76	$56.75	$56.80
Purchase #5	$148.42	11.375%	$165.3028	$165.30	$165.30	$165.30
Purchase #6	$159.25	12.640%	$179.3792	$179.38	$179.40	$179.40
Purchase #7	$236.90	10.388%	$261.5092	$261.51	$261.50	$261.50
7 purchase totals =	$1,037.36		$1,129.3623	$1,129.37	$1,129.35	$1,129.40