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	$131.50	10.225%	$144.9459	$144.95	$144.95	$144.90
Purchase #2	$246.53	10.282%	$271.8782	$271.88	$271.90	$271.90
Purchase #3	$41.89	9.192%	$45.7405	$45.74	$45.75	$45.70
Purchase #4	$11.92	4.110%	$12.4099	$12.41	$12.40	$12.40
Purchase #5	$72.84	11.389%	$81.1357	$81.14	$81.15	$81.10
Purchase #6	$112.39	13.762%	$127.8571	$127.86	$127.85	$127.90
Purchase #7	$113.69	5.179%	$119.578	$119.58	$119.60	$119.60
7 purchase totals =	$730.76		$803.5453	$803.56	$803.60	$803.50