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	$158.97	13.822%	$180.9428	$180.94	$180.95	$180.90
Purchase #2	$147.34	12.576%	$165.8695	$165.87	$165.85	$165.90
Purchase #3	$187.76	6.755%	$200.4432	$200.44	$200.45	$200.40
Purchase #4	$175.63	8.734%	$190.9695	$190.97	$190.95	$191.00
Purchase #5	$227.72	4.652%	$238.3135	$238.31	$238.30	$238.30
Purchase #6	$128.85	11.622%	$143.8249	$143.82	$143.80	$143.80
Purchase #7	$171.67	10.705%	$190.0473	$190.05	$190.05	$190.00
7 purchase totals =	$1,197.94		$1,310.4107	$1,310.40	$1,310.35	$1,310.30