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	$214.62	11.276%	$238.8206	$238.82	$238.80	$238.80
Purchase #2	$34.62	11.832%	$38.7162	$38.72	$38.70	$38.70
Purchase #3	$188.37	13.243%	$213.3158	$213.32	$213.30	$213.30
Purchase #4	$45.60	7.211%	$48.8882	$48.89	$48.90	$48.90
Purchase #5	$27.55	13.505%	$31.2706	$31.27	$31.25	$31.30
Purchase #6	$103.37	8.842%	$112.51	$112.51	$112.50	$112.50
Purchase #7	$218.45	12.132%	$244.9524	$244.95	$244.95	$245.00
7 purchase totals =	$832.58		$928.4738	$928.48	$928.40	$928.50