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	$184.86	5.517%	$195.0587	$195.06	$195.05	$195.10
Purchase #2	$133.86	11.286%	$148.9674	$148.97	$148.95	$149.00
Purchase #3	$122.25	13.848%	$139.1792	$139.18	$139.20	$139.20
Purchase #4	$243.32	12.635%	$274.0635	$274.06	$274.05	$274.10
Purchase #5	$99.25	12.322%	$111.4796	$111.48	$111.50	$111.50
Purchase #6	$149.40	4.721%	$156.4532	$156.45	$156.45	$156.50
Purchase #7	$237.96	5.337%	$250.6599	$250.66	$250.65	$250.70
7 purchase totals =	$1,170.90		$1,275.8615	$1,275.86	$1,275.85	$1,276.10