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	$169.82	11.457%	$189.2763	$189.28	$189.30	$189.30
Purchase #2	$92.34	3.304%	$95.3909	$95.39	$95.40	$95.40
Purchase #3	$68.55	4.273%	$71.4791	$71.48	$71.50	$71.50
Purchase #4	$39.69	7.803%	$42.787	$42.79	$42.80	$42.80
Purchase #5	$104.39	13.180%	$118.1486	$118.15	$118.15	$118.10
Purchase #6	$208.67	6.380%	$221.9831	$221.98	$222.00	$222.00
Purchase #7	$133.32	11.271%	$148.3465	$148.35	$148.35	$148.30
7 purchase totals =	$816.78		$887.4115	$887.42	$887.50	$887.40