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	$141.32	6.866%	$151.023	$151.02	$151.00	$151.00
Purchase #2	$147.59	7.266%	$158.3139	$158.31	$158.30	$158.30
Purchase #3	$156.37	7.171%	$167.5833	$167.58	$167.60	$167.60
Purchase #4	$237.98	10.505%	$262.9798	$262.98	$263.00	$263.00
Purchase #5	$227.45	8.820%	$247.5111	$247.51	$247.50	$247.50
Purchase #6	$52.45	11.277%	$58.3648	$58.36	$58.35	$58.40
Purchase #7	$47.78	8.630%	$51.9034	$51.90	$51.90	$51.90
7 purchase totals =	$1,010.94		$1,097.6793	$1,097.66	$1,097.65	$1,097.70