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	$212.25	3.347%	$219.354	$219.35	$219.35	$219.40
Purchase #2	$64.31	12.133%	$72.1127	$72.11	$72.10	$72.10
Purchase #3	$149.59	12.840%	$168.7974	$168.80	$168.80	$168.80
Purchase #4	$113.77	3.612%	$117.8794	$117.88	$117.90	$117.90
Purchase #5	$155.89	13.152%	$176.3927	$176.39	$176.40	$176.40
Purchase #6	$99.95	9.107%	$109.0524	$109.05	$109.05	$109.10
Purchase #7	$60.87	3.406%	$62.9432	$62.94	$62.95	$62.90
7 purchase totals =	$856.63		$926.5318	$926.52	$926.55	$926.60