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	$186.85	5.240%	$196.6409	$196.64	$196.65	$196.60
Purchase #2	$19.95	13.462%	$22.6357	$22.64	$22.65	$22.60
Purchase #3	$117.77	11.366%	$131.1557	$131.16	$131.15	$131.20
Purchase #4	$125.53	7.278%	$134.6661	$134.67	$134.65	$134.70
Purchase #5	$96.66	7.541%	$103.9491	$103.95	$103.95	$103.90
Purchase #6	$49.75	12.221%	$55.8299	$55.83	$55.85	$55.80
Purchase #7	$186.63	5.181%	$196.2993	$196.30	$196.30	$196.30
7 purchase totals =	$783.14		$841.1767	$841.19	$841.20	$841.10