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	$99.32	12.654%	$111.888	$111.89	$111.90	$111.90
Purchase #2	$57.55	7.329%	$61.7678	$61.77	$61.75	$61.80
Purchase #3	$92.57	12.619%	$104.2514	$104.25	$104.25	$104.30
Purchase #4	$228.88	4.681%	$239.5939	$239.59	$239.60	$239.60
Purchase #5	$244.72	12.598%	$275.5498	$275.55	$275.55	$275.50
Purchase #6	$187.84	8.133%	$203.117	$203.12	$203.10	$203.10
Purchase #7	$163.71	3.871%	$170.0472	$170.05	$170.05	$170.00
7 purchase totals =	$1,074.59		$1,166.2151	$1,166.22	$1,166.20	$1,166.20