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	$247.37	11.288%	$275.2931	$275.29	$275.30	$275.30
Purchase #2	$150.47	4.364%	$157.0365	$157.04	$157.05	$157.00
Purchase #3	$76.38	9.820%	$83.8805	$83.88	$83.90	$83.90
Purchase #4	$159.96	4.118%	$166.5472	$166.55	$166.55	$166.50
Purchase #5	$199.82	11.132%	$222.064	$222.06	$222.05	$222.10
Purchase #6	$9.63	4.601%	$10.0731	$10.07	$10.05	$10.10
Purchase #7	$93.70	5.212%	$98.5836	$98.58	$98.60	$98.60
7 purchase totals =	$937.33		$1,013.4780	$1,013.47	$1,013.50	$1,013.50