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	$45.39	6.783%	$48.4688	$48.47	$48.45	$48.50
Purchase #2	$90.43	5.562%	$95.4597	$95.46	$95.45	$95.50
Purchase #3	$248.55	5.783%	$262.9236	$262.92	$262.90	$262.90
Purchase #4	$98.61	9.378%	$107.8576	$107.86	$107.85	$107.90
Purchase #5	$215.88	12.619%	$243.1219	$243.12	$243.10	$243.10
Purchase #6	$240.36	9.813%	$263.9465	$263.95	$263.95	$263.90
Purchase #7	$111.56	11.617%	$124.5199	$124.52	$124.50	$124.50
7 purchase totals =	$1,050.78		$1,146.2980	$1,146.30	$1,146.20	$1,146.30