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	$115.34	7.158%	$123.596	$123.60	$123.60	$123.60
Purchase #2	$236.59	9.678%	$259.4872	$259.49	$259.50	$259.50
Purchase #3	$18.52	11.765%	$20.6989	$20.70	$20.70	$20.70
Purchase #4	$172.55	9.238%	$188.4902	$188.49	$188.50	$188.50
Purchase #5	$118.53	10.844%	$131.3834	$131.38	$131.40	$131.40
Purchase #6	$231.76	5.404%	$244.2843	$244.28	$244.30	$244.30
Purchase #7	$232.92	4.581%	$243.5901	$243.59	$243.60	$243.60
7 purchase totals =	$1,126.21		$1,211.5301	$1,211.53	$1,211.60	$1,211.60