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	$150.34	10.627%	$166.3166	$166.32	$166.30	$166.30
Purchase #2	$172.54	11.564%	$192.4925	$192.49	$192.50	$192.50
Purchase #3	$46.78	8.772%	$50.8835	$50.88	$50.90	$50.90
Purchase #4	$84.80	7.503%	$91.1625	$91.16	$91.15	$91.20
Purchase #5	$56.79	10.583%	$62.8001	$62.80	$62.80	$62.80
Purchase #6	$94.67	7.477%	$101.7485	$101.75	$101.75	$101.70
Purchase #7	$50.72	10.208%	$55.8975	$55.90	$55.90	$55.90
7 purchase totals =	$656.64		$721.3012	$721.30	$721.30	$721.30