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	$42.27	11.406%	$47.0913	$47.09	$47.10	$47.10
Purchase #2	$67.47	6.766%	$72.035	$72.04	$72.05	$72.00
Purchase #3	$82.35	9.275%	$89.988	$89.99	$90.00	$90.00
Purchase #4	$175.27	7.593%	$188.5783	$188.58	$188.60	$188.60
Purchase #5	$167.59	11.558%	$186.9601	$186.96	$186.95	$187.00
Purchase #6	$204.29	8.294%	$221.2338	$221.23	$221.25	$221.20
Purchase #7	$223.55	10.808%	$247.7113	$247.71	$247.70	$247.70
7 purchase totals =	$962.79		$1,053.5978	$1,053.60	$1,053.65	$1,053.60