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	$233.34	12.153%	$261.6978	$261.70	$261.70	$261.70
Purchase #2	$98.55	12.657%	$111.0235	$111.02	$111.00	$111.00
Purchase #3	$132.27	4.270%	$137.9179	$137.92	$137.90	$137.90
Purchase #4	$159.31	11.736%	$178.0066	$178.01	$178.00	$178.00
Purchase #5	$91.77	9.816%	$100.7781	$100.78	$100.80	$100.80
Purchase #6	$194.85	13.506%	$221.1664	$221.17	$221.15	$221.20
Purchase #7	$226.43	13.246%	$256.4229	$256.42	$256.40	$256.40
7 purchase totals =	$1,136.52		$1,267.0132	$1,267.02	$1,266.95	$1,267.00