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	$228.36	8.266%	$247.2362	$247.24	$247.25	$247.20
Purchase #2	$197.62	7.844%	$213.1213	$213.12	$213.10	$213.10
Purchase #3	$89.41	11.700%	$99.871	$99.87	$99.85	$99.90
Purchase #4	$17.47	12.853%	$19.7154	$19.72	$19.70	$19.70
Purchase #5	$27.69	13.512%	$31.4315	$31.43	$31.45	$31.40
Purchase #6	$71.63	9.638%	$78.5337	$78.53	$78.55	$78.50
Purchase #7	$167.55	5.355%	$176.5223	$176.52	$176.50	$176.50
7 purchase totals =	$799.73		$866.4314	$866.43	$866.40	$866.30