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	$171.82	7.736%	$185.112	$185.11	$185.10	$185.10
Purchase #2	$197.84	12.641%	$222.849	$222.85	$222.85	$222.80
Purchase #3	$48.78	4.300%	$50.8775	$50.88	$50.90	$50.90
Purchase #4	$173.48	8.503%	$188.231	$188.23	$188.25	$188.20
Purchase #5	$225.81	4.285%	$235.486	$235.49	$235.50	$235.50
Purchase #6	$99.64	4.681%	$104.3041	$104.30	$104.30	$104.30
Purchase #7	$238.51	4.638%	$249.5721	$249.57	$249.55	$249.60
7 purchase totals =	$1,155.88		$1,236.4317	$1,236.43	$1,236.45	$1,236.40