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	$22.58	5.714%	$23.8702	$23.87	$23.85	$23.90
Purchase #2	$70.28	3.188%	$72.5205	$72.52	$72.50	$72.50
Purchase #3	$6.61	10.440%	$7.3001	$7.30	$7.30	$7.30
Purchase #4	$202.31	9.487%	$221.5031	$221.50	$221.50	$221.50
Purchase #5	$64.89	8.356%	$70.3122	$70.31	$70.30	$70.30
Purchase #6	$116.72	3.556%	$120.8706	$120.87	$120.85	$120.90
Purchase #7	$185.79	12.424%	$208.8725	$208.87	$208.85	$208.90
7 purchase totals =	$669.18		$725.2492	$725.24	$725.15	$725.30