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	$40.54	13.187%	$45.886	$45.89	$45.90	$45.90
Purchase #2	$34.59	5.255%	$36.4077	$36.41	$36.40	$36.40
Purchase #3	$59.79	3.764%	$62.0405	$62.04	$62.05	$62.00
Purchase #4	$39.42	10.386%	$43.5142	$43.51	$43.50	$43.50
Purchase #5	$196.86	13.459%	$223.3554	$223.36	$223.35	$223.40
Purchase #6	$250.68	5.164%	$263.6251	$263.63	$263.65	$263.60
Purchase #7	$100.95	9.825%	$110.8683	$110.87	$110.85	$110.90
7 purchase totals =	$722.83		$785.6972	$785.71	$785.70	$785.70