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	$67.64	7.317%	$72.5892	$72.59	$72.60	$72.60
Purchase #2	$56.57	8.759%	$61.525	$61.53	$61.55	$61.50
Purchase #3	$173.37	3.782%	$179.9269	$179.93	$179.95	$179.90
Purchase #4	$244.42	12.742%	$275.564	$275.56	$275.55	$275.60
Purchase #5	$224.79	7.781%	$242.2809	$242.28	$242.30	$242.30
Purchase #6	$248.96	7.655%	$268.0179	$268.02	$268.00	$268.00
Purchase #7	$155.29	6.473%	$165.3419	$165.34	$165.35	$165.30
7 purchase totals =	$1,171.04		$1,265.2458	$1,265.25	$1,265.30	$1,265.20