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	$72.74	3.390%	$75.2059	$75.21	$75.20	$75.20
Purchase #2	$11.71	11.522%	$13.0592	$13.06	$13.05	$13.10
Purchase #3	$96.85	4.104%	$100.8247	$100.82	$100.80	$100.80
Purchase #4	$103.50	7.792%	$111.5647	$111.56	$111.55	$111.60
Purchase #5	$186.38	11.659%	$208.11	$208.11	$208.10	$208.10
Purchase #6	$184.84	8.352%	$200.2778	$200.28	$200.30	$200.30
Purchase #7	$172.97	4.145%	$180.1396	$180.14	$180.15	$180.10
7 purchase totals =	$828.99		$889.1819	$889.18	$889.15	$889.20