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	$180.25	9.199%	$196.8312	$196.83	$196.85	$196.80
Purchase #2	$11.85	10.596%	$13.1056	$13.11	$13.10	$13.10
Purchase #3	$113.89	7.357%	$122.2689	$122.27	$122.25	$122.30
Purchase #4	$143.54	9.475%	$157.1404	$157.14	$157.15	$157.10
Purchase #5	$80.87	10.242%	$89.1527	$89.15	$89.15	$89.20
Purchase #6	$71.99	8.118%	$77.8341	$77.83	$77.85	$77.80
Purchase #7	$30.91	9.465%	$33.8356	$33.84	$33.85	$33.80
7 purchase totals =	$633.30		$690.1685	$690.17	$690.20	$690.10