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	$129.59	10.797%	$143.5818	$143.58	$143.60	$143.60
Purchase #2	$201.86	4.811%	$211.5715	$211.57	$211.55	$211.60
Purchase #3	$140.76	8.621%	$152.8949	$152.89	$152.90	$152.90
Purchase #4	$243.78	9.606%	$267.1975	$267.20	$267.20	$267.20
Purchase #5	$248.59	11.530%	$277.2524	$277.25	$277.25	$277.30
Purchase #6	$138.52	4.169%	$144.2949	$144.29	$144.30	$144.30
Purchase #7	$99.29	4.613%	$103.8702	$103.87	$103.85	$103.90
7 purchase totals =	$1,202.39		$1,300.6632	$1,300.65	$1,300.65	$1,300.80