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	$67.84	5.365%	$71.4796	$71.48	$71.50	$71.50
Purchase #2	$191.81	10.846%	$212.6137	$212.61	$212.60	$212.60
Purchase #3	$208.62	10.316%	$230.1412	$230.14	$230.15	$230.10
Purchase #4	$126.56	8.871%	$137.7871	$137.79	$137.80	$137.80
Purchase #5	$73.75	6.873%	$78.8188	$78.82	$78.80	$78.80
Purchase #6	$213.68	12.740%	$240.9028	$240.90	$240.90	$240.90
Purchase #7	$47.60	10.351%	$52.5271	$52.53	$52.55	$52.50
7 purchase totals =	$929.86		$1,024.2703	$1,024.27	$1,024.30	$1,024.20