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	$43.66	13.635%	$49.613	$49.61	$49.60	$49.60
Purchase #2	$223.44	12.700%	$251.8169	$251.82	$251.80	$251.80
Purchase #3	$215.64	12.873%	$243.3993	$243.40	$243.40	$243.40
Purchase #4	$236.94	11.680%	$264.6146	$264.61	$264.60	$264.60
Purchase #5	$163.33	5.508%	$172.3262	$172.33	$172.35	$172.30
Purchase #6	$152.81	10.367%	$168.6518	$168.65	$168.65	$168.70
Purchase #7	$44.52	12.641%	$50.1478	$50.15	$50.15	$50.10
7 purchase totals =	$1,080.34		$1,200.5696	$1,200.57	$1,200.55	$1,200.50