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	$80.52	6.686%	$85.9036	$85.90	$85.90	$85.90
Purchase #2	$141.63	3.597%	$146.7244	$146.72	$146.70	$146.70
Purchase #3	$42.31	10.114%	$46.5892	$46.59	$46.60	$46.60
Purchase #4	$58.90	6.620%	$62.7992	$62.80	$62.80	$62.80
Purchase #5	$191.35	6.500%	$203.7878	$203.79	$203.80	$203.80
Purchase #6	$98.34	3.180%	$101.4672	$101.47	$101.45	$101.50
Purchase #7	$55.52	13.207%	$62.8525	$62.85	$62.85	$62.90
7 purchase totals =	$668.57		$710.1239	$710.12	$710.10	$710.20