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	$178.47	3.164%	$184.1168	$184.12	$184.10	$184.10
Purchase #2	$244.71	13.590%	$277.9661	$277.97	$277.95	$278.00
Purchase #3	$52.47	3.793%	$54.4602	$54.46	$54.45	$54.50
Purchase #4	$191.95	4.683%	$200.939	$200.94	$200.95	$200.90
Purchase #5	$110.35	11.701%	$123.2621	$123.26	$123.25	$123.30
Purchase #6	$182.95	4.716%	$191.5779	$191.58	$191.60	$191.60
Purchase #7	$98.75	12.797%	$111.387	$111.39	$111.40	$111.40
7 purchase totals =	$1,059.65		$1,143.7091	$1,143.72	$1,143.70	$1,143.80