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	$107.40	3.495%	$111.1536	$111.15	$111.15	$111.20
Purchase #2	$139.63	6.368%	$148.5216	$148.52	$148.50	$148.50
Purchase #3	$209.26	10.319%	$230.8535	$230.85	$230.85	$230.90
Purchase #4	$55.76	10.251%	$61.476	$61.48	$61.50	$61.50
Purchase #5	$206.89	13.331%	$234.4705	$234.47	$234.45	$234.50
Purchase #6	$151.80	10.858%	$168.2824	$168.28	$168.30	$168.30
Purchase #7	$132.72	11.706%	$148.2562	$148.26	$148.25	$148.30
7 purchase totals =	$1,003.46		$1,103.0138	$1,103.01	$1,103.00	$1,103.20