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	$168.96	4.681%	$176.869	$176.87	$176.85	$176.90
Purchase #2	$171.91	11.360%	$191.439	$191.44	$191.45	$191.40
Purchase #3	$90.51	11.269%	$100.7096	$100.71	$100.70	$100.70
Purchase #4	$96.88	13.694%	$110.1467	$110.15	$110.15	$110.10
Purchase #5	$47.66	10.604%	$52.7139	$52.71	$52.70	$52.70
Purchase #6	$128.89	3.644%	$133.5868	$133.59	$133.60	$133.60
Purchase #7	$98.83	8.111%	$106.8461	$106.85	$106.85	$106.80
7 purchase totals =	$803.64		$872.3111	$872.32	$872.30	$872.20