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	$229.60	8.227%	$248.4892	$248.49	$248.50	$248.50
Purchase #2	$195.27	4.254%	$203.5768	$203.58	$203.60	$203.60
Purchase #3	$44.46	3.281%	$45.9187	$45.92	$45.90	$45.90
Purchase #4	$113.77	10.682%	$125.9229	$125.92	$125.90	$125.90
Purchase #5	$139.92	8.408%	$151.6845	$151.68	$151.70	$151.70
Purchase #6	$173.59	13.152%	$196.4206	$196.42	$196.40	$196.40
Purchase #7	$100.48	9.801%	$110.328	$110.33	$110.35	$110.30
7 purchase totals =	$997.09		$1,082.3407	$1,082.34	$1,082.35	$1,082.30