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	$168.72	13.386%	$191.3049	$191.30	$191.30	$191.30
Purchase #2	$36.32	5.847%	$38.4436	$38.44	$38.45	$38.40
Purchase #3	$46.87	3.734%	$48.6201	$48.62	$48.60	$48.60
Purchase #4	$195.97	7.592%	$210.848	$210.85	$210.85	$210.80
Purchase #5	$82.81	9.366%	$90.566	$90.57	$90.55	$90.60
Purchase #6	$139.58	8.261%	$151.1107	$151.11	$151.10	$151.10
Purchase #7	$97.47	4.197%	$101.5608	$101.56	$101.55	$101.60
7 purchase totals =	$767.74		$832.4541	$832.45	$832.40	$832.40