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	$185.75	10.822%	$205.8519	$205.85	$205.85	$205.90
Purchase #2	$239.48	13.516%	$271.8481	$271.85	$271.85	$271.80
Purchase #3	$176.56	9.467%	$193.2749	$193.27	$193.25	$193.30
Purchase #4	$128.67	4.611%	$134.603	$134.60	$134.60	$134.60
Purchase #5	$175.77	9.117%	$191.795	$191.80	$191.80	$191.80
Purchase #6	$246.27	3.657%	$255.2761	$255.28	$255.30	$255.30
Purchase #7	$196.46	13.297%	$222.5833	$222.58	$222.60	$222.60
7 purchase totals =	$1,348.96		$1,475.2323	$1,475.23	$1,475.25	$1,475.30