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	$31.90	3.241%	$32.9339	$32.93	$32.95	$32.90
Purchase #2	$240.55	6.374%	$255.8827	$255.88	$255.90	$255.90
Purchase #3	$90.79	13.650%	$103.1828	$103.18	$103.20	$103.20
Purchase #4	$90.55	6.773%	$96.683	$96.68	$96.70	$96.70
Purchase #5	$197.96	3.110%	$204.1166	$204.12	$204.10	$204.10
Purchase #6	$236.98	8.189%	$256.3863	$256.39	$256.40	$256.40
Purchase #7	$96.46	5.238%	$101.5126	$101.51	$101.50	$101.50
7 purchase totals =	$985.19		$1,050.6979	$1,050.69	$1,050.75	$1,050.70