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	$77.66	6.688%	$82.8539	$82.85	$82.85	$82.90
Purchase #2	$244.35	4.141%	$254.4685	$254.47	$254.45	$254.50
Purchase #3	$76.64	11.517%	$85.4666	$85.47	$85.45	$85.50
Purchase #4	$18.80	9.247%	$20.5384	$20.54	$20.55	$20.50
Purchase #5	$191.92	10.225%	$211.5438	$211.54	$211.55	$211.50
Purchase #6	$250.94	12.142%	$281.4091	$281.41	$281.40	$281.40
Purchase #7	$155.35	10.847%	$172.2008	$172.20	$172.20	$172.20
7 purchase totals =	$1,015.66		$1,108.4811	$1,108.48	$1,108.45	$1,108.50