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	$56.26	9.765%	$61.7538	$61.75	$61.75	$61.80
Purchase #2	$165.88	8.237%	$179.5435	$179.54	$179.55	$179.50
Purchase #3	$120.45	3.653%	$124.85	$124.85	$124.85	$124.90
Purchase #4	$159.48	3.387%	$164.8816	$164.88	$164.90	$164.90
Purchase #5	$100.54	9.863%	$110.4563	$110.46	$110.45	$110.50
Purchase #6	$96.37	5.772%	$101.9325	$101.93	$101.95	$101.90
Purchase #7	$88.97	3.570%	$92.1462	$92.15	$92.15	$92.10
7 purchase totals =	$787.95		$835.5639	$835.56	$835.60	$835.60