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	$143.93	3.667%	$149.2079	$149.21	$149.20	$149.20
Purchase #2	$182.47	11.731%	$203.8756	$203.88	$203.90	$203.90
Purchase #3	$100.98	13.186%	$114.2952	$114.30	$114.30	$114.30
Purchase #4	$135.33	10.271%	$149.2297	$149.23	$149.25	$149.20
Purchase #5	$138.82	8.345%	$150.4045	$150.40	$150.40	$150.40
Purchase #6	$53.89	10.165%	$59.3679	$59.37	$59.35	$59.40
Purchase #7	$168.83	3.729%	$175.1257	$175.13	$175.15	$175.10
7 purchase totals =	$924.25		$1,001.5065	$1,001.52	$1,001.55	$1,001.50