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	$101.47	10.357%	$111.9792	$111.98	$112.00	$112.00
Purchase #2	$79.40	4.612%	$83.0619	$83.06	$83.05	$83.10
Purchase #3	$162.49	13.181%	$183.9078	$183.91	$183.90	$183.90
Purchase #4	$26.27	4.770%	$27.5231	$27.52	$27.50	$27.50
Purchase #5	$138.52	9.855%	$152.1711	$152.17	$152.15	$152.20
Purchase #6	$81.74	7.609%	$87.9596	$87.96	$87.95	$88.00
Purchase #7	$99.88	8.799%	$108.6684	$108.67	$108.65	$108.70
7 purchase totals =	$689.77		$755.2711	$755.27	$755.20	$755.40