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	$131.69	12.781%	$148.5213	$148.52	$148.50	$148.50
Purchase #2	$13.26	5.246%	$13.9556	$13.96	$13.95	$14.00
Purchase #3	$29.52	12.351%	$33.166	$33.17	$33.15	$33.20
Purchase #4	$206.95	7.565%	$222.6058	$222.61	$222.60	$222.60
Purchase #5	$200.41	10.585%	$221.6234	$221.62	$221.60	$221.60
Purchase #6	$67.74	4.131%	$70.5383	$70.54	$70.55	$70.50
Purchase #7	$151.69	11.686%	$169.4165	$169.42	$169.40	$169.40
7 purchase totals =	$801.26		$879.8269	$879.84	$879.75	$879.80