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	$148.88	13.586%	$169.1068	$169.11	$169.10	$169.10
Purchase #2	$14.27	6.671%	$15.222	$15.22	$15.20	$15.20
Purchase #3	$116.31	7.348%	$124.8565	$124.86	$124.85	$124.90
Purchase #4	$191.32	6.763%	$204.259	$204.26	$204.25	$204.30
Purchase #5	$122.88	13.464%	$139.4246	$139.42	$139.40	$139.40
Purchase #6	$72.54	8.368%	$78.6101	$78.61	$78.60	$78.60
Purchase #7	$143.63	11.607%	$160.3011	$160.30	$160.30	$160.30
7 purchase totals =	$809.83		$891.7801	$891.78	$891.70	$891.80