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	$78.91	8.543%	$85.6513	$85.65	$85.65	$85.70
Purchase #2	$51.63	8.746%	$56.1456	$56.15	$56.15	$56.10
Purchase #3	$224.72	5.534%	$237.156	$237.16	$237.15	$237.20
Purchase #4	$153.67	7.767%	$165.6055	$165.61	$165.60	$165.60
Purchase #5	$118.55	9.665%	$130.0079	$130.01	$130.00	$130.00
Purchase #6	$200.29	5.842%	$211.9909	$211.99	$212.00	$212.00
Purchase #7	$85.82	4.656%	$89.8158	$89.82	$89.80	$89.80
7 purchase totals =	$913.59		$976.3730	$976.39	$976.35	$976.40