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	$244.81	6.601%	$260.9699	$260.97	$260.95	$261.00
Purchase #2	$250.82	11.417%	$279.4561	$279.46	$279.45	$279.50
Purchase #3	$160.42	4.171%	$167.1111	$167.11	$167.10	$167.10
Purchase #4	$237.93	4.551%	$248.7582	$248.76	$248.75	$248.80
Purchase #5	$28.29	10.627%	$31.2964	$31.30	$31.30	$31.30
Purchase #6	$40.92	11.444%	$45.6029	$45.60	$45.60	$45.60
Purchase #7	$119.29	8.596%	$129.5442	$129.54	$129.55	$129.50
7 purchase totals =	$1,082.48		$1,162.7388	$1,162.74	$1,162.70	$1,162.80