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	$134.72	5.499%	$142.1283	$142.13	$142.15	$142.10
Purchase #2	$152.30	8.571%	$165.3536	$165.35	$165.35	$165.40
Purchase #3	$222.84	8.203%	$241.1196	$241.12	$241.10	$241.10
Purchase #4	$51.89	6.721%	$55.3775	$55.38	$55.40	$55.40
Purchase #5	$157.70	6.604%	$168.1145	$168.11	$168.10	$168.10
Purchase #6	$135.57	4.396%	$141.5297	$141.53	$141.55	$141.50
Purchase #7	$72.91	8.105%	$78.8194	$78.82	$78.80	$78.80
7 purchase totals =	$927.93		$992.4426	$992.44	$992.45	$992.40