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	$214.28	6.780%	$228.8082	$228.81	$228.80	$228.80
Purchase #2	$123.61	7.707%	$133.1366	$133.14	$133.15	$133.10
Purchase #3	$99.69	4.818%	$104.4931	$104.49	$104.50	$104.50
Purchase #4	$227.27	13.707%	$258.4219	$258.42	$258.40	$258.40
Purchase #5	$130.69	10.136%	$143.9367	$143.94	$143.95	$143.90
Purchase #6	$72.40	6.660%	$77.2218	$77.22	$77.20	$77.20
Purchase #7	$85.54	12.349%	$96.1033	$96.10	$96.10	$96.10
7 purchase totals =	$953.48		$1,042.1216	$1,042.12	$1,042.10	$1,042.00