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	$151.51	4.801%	$158.784	$158.78	$158.80	$158.80
Purchase #2	$213.75	8.433%	$231.7755	$231.78	$231.80	$231.80
Purchase #3	$95.61	11.426%	$106.5344	$106.53	$106.55	$106.50
Purchase #4	$42.96	4.520%	$44.9018	$44.90	$44.90	$44.90
Purchase #5	$97.94	7.224%	$105.0152	$105.02	$105.00	$105.00
Purchase #6	$101.90	10.853%	$112.9592	$112.96	$112.95	$113.00
Purchase #7	$174.77	7.823%	$188.4423	$188.44	$188.45	$188.40
7 purchase totals =	$878.44		$948.4124	$948.41	$948.45	$948.40