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	$135.84	12.530%	$152.8608	$152.86	$152.85	$152.90
Purchase #2	$34.30	5.704%	$36.2565	$36.26	$36.25	$36.30
Purchase #3	$57.51	7.682%	$61.9279	$61.93	$61.95	$61.90
Purchase #4	$54.66	9.233%	$59.7068	$59.71	$59.70	$59.70
Purchase #5	$156.38	9.403%	$171.0844	$171.08	$171.10	$171.10
Purchase #6	$237.63	10.741%	$263.1538	$263.15	$263.15	$263.20
Purchase #7	$160.64	11.515%	$179.1377	$179.14	$179.15	$179.10
7 purchase totals =	$836.96		$924.1279	$924.13	$924.15	$924.20