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	$105.68	8.375%	$114.5307	$114.53	$114.55	$114.50
Purchase #2	$219.83	6.223%	$233.51	$233.51	$233.50	$233.50
Purchase #3	$175.92	7.103%	$188.4156	$188.42	$188.40	$188.40
Purchase #4	$127.79	4.340%	$133.3361	$133.34	$133.35	$133.30
Purchase #5	$114.33	7.756%	$123.1974	$123.20	$123.20	$123.20
Purchase #6	$193.90	4.754%	$203.118	$203.12	$203.10	$203.10
Purchase #7	$79.83	8.257%	$86.4216	$86.42	$86.40	$86.40
7 purchase totals =	$1,017.28		$1,082.5294	$1,082.54	$1,082.50	$1,082.40