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	$190.88	4.133%	$198.7691	$198.77	$198.75	$198.80
Purchase #2	$239.25	5.424%	$252.2269	$252.23	$252.25	$252.20
Purchase #3	$178.77	5.486%	$188.5773	$188.58	$188.60	$188.60
Purchase #4	$6.28	3.710%	$6.513	$6.51	$6.50	$6.50
Purchase #5	$153.79	11.418%	$171.3497	$171.35	$171.35	$171.30
Purchase #6	$168.89	12.571%	$190.1212	$190.12	$190.10	$190.10
Purchase #7	$78.68	8.733%	$85.5511	$85.55	$85.55	$85.60
7 purchase totals =	$1,016.54		$1,093.1083	$1,093.11	$1,093.10	$1,093.10