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	$93.26	5.866%	$98.7306	$98.73	$98.75	$98.70
Purchase #2	$228.50	8.869%	$248.7657	$248.77	$248.75	$248.80
Purchase #3	$31.49	6.861%	$33.6505	$33.65	$33.65	$33.70
Purchase #4	$17.84	3.306%	$18.4298	$18.43	$18.45	$18.40
Purchase #5	$70.55	11.735%	$78.829	$78.83	$78.85	$78.80
Purchase #6	$38.67	10.804%	$42.8479	$42.85	$42.85	$42.80
Purchase #7	$181.80	10.344%	$200.6054	$200.61	$200.60	$200.60
7 purchase totals =	$662.11		$721.8589	$721.87	$721.90	$721.80