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	$119.55	9.105%	$130.435	$130.44	$130.45	$130.40
Purchase #2	$166.39	7.227%	$178.415	$178.42	$178.40	$178.40
Purchase #3	$147.77	7.226%	$158.4479	$158.45	$158.45	$158.40
Purchase #4	$52.42	10.531%	$57.9404	$57.94	$57.95	$57.90
Purchase #5	$98.70	10.717%	$109.2777	$109.28	$109.30	$109.30
Purchase #6	$77.45	9.802%	$85.0416	$85.04	$85.05	$85.00
Purchase #7	$96.62	5.507%	$101.9409	$101.94	$101.95	$101.90
7 purchase totals =	$758.90		$821.4985	$821.51	$821.55	$821.30