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	$194.82	8.610%	$211.594	$211.59	$211.60	$211.60
Purchase #2	$186.54	12.707%	$210.2436	$210.24	$210.25	$210.20
Purchase #3	$167.35	4.278%	$174.5092	$174.51	$174.50	$174.50
Purchase #4	$238.69	11.449%	$266.0176	$266.02	$266.00	$266.00
Purchase #5	$137.59	9.667%	$150.8908	$150.89	$150.90	$150.90
Purchase #6	$168.25	6.553%	$179.2754	$179.28	$179.30	$179.30
Purchase #7	$151.88	4.385%	$158.5399	$158.54	$158.55	$158.50
7 purchase totals =	$1,245.12		$1,351.0705	$1,351.07	$1,351.10	$1,351.00