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	$147.86	9.840%	$162.4094	$162.41	$162.40	$162.40
Purchase #2	$201.41	5.543%	$212.5742	$212.57	$212.55	$212.60
Purchase #3	$149.81	3.677%	$155.3185	$155.32	$155.30	$155.30
Purchase #4	$141.85	10.139%	$156.2322	$156.23	$156.25	$156.20
Purchase #5	$120.98	9.319%	$132.2541	$132.25	$132.25	$132.30
Purchase #6	$66.85	8.168%	$72.3103	$72.31	$72.30	$72.30
Purchase #7	$33.81	10.178%	$37.2512	$37.25	$37.25	$37.30
7 purchase totals =	$862.57		$928.3499	$928.34	$928.30	$928.40