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	$134.51	5.302%	$141.6417	$141.64	$141.65	$141.60
Purchase #2	$62.42	13.703%	$70.9734	$70.97	$70.95	$71.00
Purchase #3	$40.61	7.114%	$43.499	$43.50	$43.50	$43.50
Purchase #4	$69.28	10.260%	$76.3881	$76.39	$76.40	$76.40
Purchase #5	$45.50	6.740%	$48.5667	$48.57	$48.55	$48.60
Purchase #6	$201.80	10.342%	$222.6702	$222.67	$222.65	$222.70
Purchase #7	$159.43	13.240%	$180.5385	$180.54	$180.55	$180.50
7 purchase totals =	$713.55		$784.2776	$784.28	$784.25	$784.30