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	$55.28	11.306%	$61.53	$61.53	$61.55	$61.50
Purchase #2	$13.51	3.242%	$13.948	$13.95	$13.95	$13.90
Purchase #3	$61.94	11.194%	$68.8736	$68.87	$68.85	$68.90
Purchase #4	$200.89	6.108%	$213.1604	$213.16	$213.15	$213.20
Purchase #5	$179.35	3.308%	$185.2829	$185.28	$185.30	$185.30
Purchase #6	$244.94	11.590%	$273.3285	$273.33	$273.35	$273.30
Purchase #7	$244.44	11.231%	$271.8931	$271.89	$271.90	$271.90
7 purchase totals =	$1,000.35		$1,088.0165	$1,088.01	$1,088.05	$1,088.00