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	$59.47	11.843%	$66.513	$66.51	$66.50	$66.50
Purchase #2	$85.31	5.112%	$89.671	$89.67	$89.65	$89.70
Purchase #3	$200.91	4.317%	$209.5833	$209.58	$209.60	$209.60
Purchase #4	$101.78	11.578%	$113.5641	$113.56	$113.55	$113.60
Purchase #5	$105.28	4.478%	$109.9944	$109.99	$110.00	$110.00
Purchase #6	$163.86	13.825%	$186.5136	$186.51	$186.50	$186.50
Purchase #7	$159.43	3.747%	$165.4038	$165.40	$165.40	$165.40
7 purchase totals =	$876.04		$941.2432	$941.22	$941.20	$941.30