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	$124.79	13.671%	$141.85	$141.85	$141.85	$141.90
Purchase #2	$33.65	10.397%	$37.1486	$37.15	$37.15	$37.10
Purchase #3	$50.52	4.502%	$52.7944	$52.79	$52.80	$52.80
Purchase #4	$206.69	9.771%	$226.8857	$226.89	$226.90	$226.90
Purchase #5	$90.56	3.295%	$93.544	$93.54	$93.55	$93.50
Purchase #6	$82.53	10.645%	$91.3153	$91.32	$91.30	$91.30
Purchase #7	$123.89	7.463%	$133.1359	$133.14	$133.15	$133.10
7 purchase totals =	$712.63		$776.6739	$776.68	$776.70	$776.60