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	$95.54	3.862%	$99.2298	$99.23	$99.25	$99.20
Purchase #2	$226.90	3.804%	$235.5313	$235.53	$235.55	$235.50
Purchase #3	$55.25	10.201%	$60.8861	$60.89	$60.90	$60.90
Purchase #4	$164.25	9.131%	$179.2477	$179.25	$179.25	$179.20
Purchase #5	$243.92	7.799%	$262.9433	$262.94	$262.95	$262.90
Purchase #6	$103.94	7.774%	$112.0203	$112.02	$112.00	$112.00
Purchase #7	$54.36	13.806%	$61.8649	$61.86	$61.85	$61.90
7 purchase totals =	$944.16		$1,011.7234	$1,011.72	$1,011.75	$1,011.60