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	$131.53	7.297%	$141.1277	$141.13	$141.15	$141.10
Purchase #2	$248.39	12.682%	$279.8908	$279.89	$279.90	$279.90
Purchase #3	$59.30	4.474%	$61.9531	$61.95	$61.95	$62.00
Purchase #4	$181.98	5.229%	$191.4957	$191.50	$191.50	$191.50
Purchase #5	$250.38	3.219%	$258.4397	$258.44	$258.45	$258.40
Purchase #6	$123.55	7.302%	$132.5716	$132.57	$132.55	$132.60
Purchase #7	$91.93	13.602%	$104.4343	$104.43	$104.45	$104.40
7 purchase totals =	$1,087.06		$1,169.9129	$1,169.91	$1,169.95	$1,169.90