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	$241.46	10.843%	$267.6415	$267.64	$267.65	$267.60
Purchase #2	$237.62	11.539%	$265.039	$265.04	$265.05	$265.00
Purchase #3	$154.66	8.770%	$168.2237	$168.22	$168.20	$168.20
Purchase #4	$9.48	9.642%	$10.3941	$10.39	$10.40	$10.40
Purchase #5	$122.55	4.672%	$128.2755	$128.28	$128.30	$128.30
Purchase #6	$159.48	3.736%	$165.4382	$165.44	$165.45	$165.40
Purchase #7	$85.72	7.168%	$91.8644	$91.86	$91.85	$91.90
7 purchase totals =	$1,010.97		$1,096.8764	$1,096.87	$1,096.90	$1,096.80