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	$68.76	4.107%	$71.584	$71.58	$71.60	$71.60
Purchase #2	$91.69	6.270%	$97.439	$97.44	$97.45	$97.40
Purchase #3	$152.35	11.508%	$169.8824	$169.88	$169.90	$169.90
Purchase #4	$16.42	11.142%	$18.2495	$18.25	$18.25	$18.20
Purchase #5	$55.75	6.566%	$59.4105	$59.41	$59.40	$59.40
Purchase #6	$113.37	7.144%	$121.4692	$121.47	$121.45	$121.50
Purchase #7	$221.39	3.279%	$228.6494	$228.65	$228.65	$228.60
7 purchase totals =	$719.73		$766.6840	$766.68	$766.70	$766.60