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	$173.76	13.143%	$196.5973	$196.60	$196.60	$196.60
Purchase #2	$175.94	8.455%	$190.8157	$190.82	$190.80	$190.80
Purchase #3	$116.38	11.435%	$129.6881	$129.69	$129.70	$129.70
Purchase #4	$148.42	11.492%	$165.4764	$165.48	$165.50	$165.50
Purchase #5	$38.87	6.443%	$41.3744	$41.37	$41.35	$41.40
Purchase #6	$240.57	3.346%	$248.6195	$248.62	$248.60	$248.60
Purchase #7	$98.51	5.312%	$103.7429	$103.74	$103.75	$103.70
7 purchase totals =	$992.45		$1,076.3143	$1,076.32	$1,076.30	$1,076.30