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	$169.60	11.269%	$188.7122	$188.71	$188.70	$188.70
Purchase #2	$35.71	9.331%	$39.0421	$39.04	$39.05	$39.00
Purchase #3	$26.37	5.453%	$27.808	$27.81	$27.80	$27.80
Purchase #4	$139.80	9.573%	$153.1831	$153.18	$153.20	$153.20
Purchase #5	$120.25	9.418%	$131.5751	$131.58	$131.60	$131.60
Purchase #6	$42.27	3.661%	$43.8175	$43.82	$43.80	$43.80
Purchase #7	$160.89	13.610%	$182.7871	$182.79	$182.80	$182.80
7 purchase totals =	$694.89		$766.9251	$766.93	$766.95	$766.90