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	$211.50	8.275%	$229.0016	$229.00	$229.00	$229.00
Purchase #2	$179.78	4.344%	$187.5896	$187.59	$187.60	$187.60
Purchase #3	$86.68	4.692%	$90.747	$90.75	$90.75	$90.70
Purchase #4	$145.75	7.481%	$156.6536	$156.65	$156.65	$156.70
Purchase #5	$150.81	11.559%	$168.2421	$168.24	$168.25	$168.20
Purchase #6	$72.93	11.863%	$81.5817	$81.58	$81.60	$81.60
Purchase #7	$10.76	6.600%	$11.4702	$11.47	$11.45	$11.50
7 purchase totals =	$858.21		$925.2858	$925.28	$925.30	$925.30