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	$74.54	7.232%	$79.9307	$79.93	$79.95	$79.90
Purchase #2	$31.61	3.156%	$32.6076	$32.61	$32.60	$32.60
Purchase #3	$213.94	12.853%	$241.4377	$241.44	$241.45	$241.40
Purchase #4	$90.83	11.281%	$101.0765	$101.08	$101.10	$101.10
Purchase #5	$58.43	4.594%	$61.1143	$61.11	$61.10	$61.10
Purchase #6	$127.51	7.539%	$137.123	$137.12	$137.10	$137.10
Purchase #7	$41.69	5.777%	$44.0984	$44.10	$44.10	$44.10
7 purchase totals =	$638.55		$697.3882	$697.39	$697.40	$697.30