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	$54.28	13.815%	$61.7788	$61.78	$61.80	$61.80
Purchase #2	$177.95	8.241%	$192.6149	$192.61	$192.60	$192.60
Purchase #3	$145.72	4.818%	$152.7408	$152.74	$152.75	$152.70
Purchase #4	$246.60	13.500%	$279.891	$279.89	$279.90	$279.90
Purchase #5	$113.44	13.561%	$128.8236	$128.82	$128.80	$128.80
Purchase #6	$119.73	8.181%	$129.5251	$129.53	$129.55	$129.50
Purchase #7	$50.46	11.161%	$56.0918	$56.09	$56.10	$56.10
7 purchase totals =	$908.18		$1,001.4660	$1,001.46	$1,001.50	$1,001.40