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	$214.69	3.224%	$221.6116	$221.61	$221.60	$221.60
Purchase #2	$177.82	10.478%	$196.452	$196.45	$196.45	$196.50
Purchase #3	$90.53	13.632%	$102.871	$102.87	$102.85	$102.90
Purchase #4	$218.34	11.830%	$244.1696	$244.17	$244.15	$244.20
Purchase #5	$176.49	4.443%	$184.3315	$184.33	$184.35	$184.30
Purchase #6	$236.32	13.669%	$268.6226	$268.62	$268.60	$268.60
Purchase #7	$39.95	7.519%	$42.9538	$42.95	$42.95	$43.00
7 purchase totals =	$1,154.14		$1,261.0121	$1,261.00	$1,260.95	$1,261.10