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	$113.47	6.580%	$120.9363	$120.94	$120.95	$120.90
Purchase #2	$85.59	4.436%	$89.3868	$89.39	$89.40	$89.40
Purchase #3	$47.67	5.248%	$50.1717	$50.17	$50.15	$50.20
Purchase #4	$94.94	11.410%	$105.7727	$105.77	$105.75	$105.80
Purchase #5	$165.42	3.687%	$171.519	$171.52	$171.50	$171.50
Purchase #6	$10.88	3.427%	$11.2529	$11.25	$11.25	$11.30
Purchase #7	$139.71	13.478%	$158.5401	$158.54	$158.55	$158.50
7 purchase totals =	$657.68		$707.5795	$707.58	$707.55	$707.60