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	$250.34	4.871%	$262.5341	$262.53	$262.55	$262.50
Purchase #2	$95.71	10.732%	$105.9816	$105.98	$106.00	$106.00
Purchase #3	$64.65	12.725%	$72.8767	$72.88	$72.90	$72.90
Purchase #4	$21.58	11.443%	$24.0494	$24.05	$24.05	$24.00
Purchase #5	$188.89	11.279%	$210.1949	$210.19	$210.20	$210.20
Purchase #6	$145.30	7.580%	$156.3137	$156.31	$156.30	$156.30
Purchase #7	$98.85	4.616%	$103.4129	$103.41	$103.40	$103.40
7 purchase totals =	$865.32		$935.3633	$935.35	$935.40	$935.30