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	$40.87	10.562%	$45.1867	$45.19	$45.20	$45.20
Purchase #2	$52.47	13.624%	$59.6185	$59.62	$59.60	$59.60
Purchase #3	$236.28	4.799%	$247.6191	$247.62	$247.60	$247.60
Purchase #4	$41.92	6.664%	$44.7135	$44.71	$44.70	$44.70
Purchase #5	$75.40	10.843%	$83.5756	$83.58	$83.60	$83.60
Purchase #6	$160.94	6.299%	$171.0776	$171.08	$171.10	$171.10
Purchase #7	$74.46	10.247%	$82.0899	$82.09	$82.10	$82.10
7 purchase totals =	$682.34		$733.8809	$733.89	$733.90	$733.90