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	$67.69	6.625%	$72.1745	$72.17	$72.15	$72.20
Purchase #2	$97.49	3.499%	$100.9012	$100.90	$100.90	$100.90
Purchase #3	$88.31	9.251%	$96.4796	$96.48	$96.50	$96.50
Purchase #4	$87.98	9.670%	$96.4877	$96.49	$96.50	$96.50
Purchase #5	$104.33	3.684%	$108.1735	$108.17	$108.15	$108.20
Purchase #6	$132.74	11.524%	$148.037	$148.04	$148.05	$148.00
Purchase #7	$95.51	10.642%	$105.6742	$105.67	$105.65	$105.70
7 purchase totals =	$674.05		$727.9277	$727.92	$727.90	$728.00