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	$33.69	8.393%	$36.5176	$36.52	$36.50	$36.50
Purchase #2	$38.47	13.409%	$43.6284	$43.63	$43.65	$43.60
Purchase #3	$83.48	7.543%	$89.7769	$89.78	$89.80	$89.80
Purchase #4	$239.74	9.318%	$262.079	$262.08	$262.10	$262.10
Purchase #5	$128.83	12.741%	$145.2442	$145.24	$145.25	$145.20
Purchase #6	$80.73	13.789%	$91.8619	$91.86	$91.85	$91.90
Purchase #7	$57.95	6.650%	$61.8037	$61.80	$61.80	$61.80
7 purchase totals =	$662.89		$730.9117	$730.91	$730.95	$730.90