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	$13.41	9.632%	$14.7017	$14.70	$14.70	$14.70
Purchase #2	$209.48	5.739%	$221.5021	$221.50	$221.50	$221.50
Purchase #3	$75.74	12.764%	$85.4075	$85.41	$85.40	$85.40
Purchase #4	$96.31	4.356%	$100.5053	$100.51	$100.50	$100.50
Purchase #5	$238.49	10.803%	$264.2541	$264.25	$264.25	$264.30
Purchase #6	$29.85	12.543%	$33.5941	$33.59	$33.60	$33.60
Purchase #7	$100.26	11.310%	$111.5994	$111.60	$111.60	$111.60
7 purchase totals =	$763.54		$831.5642	$831.56	$831.55	$831.60