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	$41.27	4.479%	$43.1185	$43.12	$43.10	$43.10
Purchase #2	$10.81	4.220%	$11.2662	$11.27	$11.25	$11.30
Purchase #3	$79.31	8.171%	$85.7904	$85.79	$85.80	$85.80
Purchase #4	$160.94	8.291%	$174.2835	$174.28	$174.30	$174.30
Purchase #5	$241.46	13.707%	$274.5569	$274.56	$274.55	$274.60
Purchase #6	$239.95	5.651%	$253.5096	$253.51	$253.50	$253.50
Purchase #7	$207.77	12.586%	$233.9199	$233.92	$233.90	$233.90
7 purchase totals =	$981.51		$1,076.4450	$1,076.45	$1,076.40	$1,076.50