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	$160.82	4.618%	$168.2467	$168.25	$168.25	$168.20
Purchase #2	$47.77	8.547%	$51.8529	$51.85	$51.85	$51.90
Purchase #3	$240.62	7.385%	$258.3898	$258.39	$258.40	$258.40
Purchase #4	$87.45	4.341%	$91.2462	$91.25	$91.25	$91.20
Purchase #5	$195.86	13.712%	$222.7163	$222.72	$222.70	$222.70
Purchase #6	$134.57	12.685%	$151.6402	$151.64	$151.65	$151.60
Purchase #7	$173.64	8.744%	$188.8231	$188.82	$188.80	$188.80
7 purchase totals =	$1,040.73		$1,132.9152	$1,132.92	$1,132.90	$1,132.80