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	$119.45	9.802%	$131.1585	$131.16	$131.15	$131.20
Purchase #2	$220.40	5.454%	$232.4206	$232.42	$232.40	$232.40
Purchase #3	$46.59	8.527%	$50.5627	$50.56	$50.55	$50.60
Purchase #4	$221.30	9.249%	$241.768	$241.77	$241.75	$241.80
Purchase #5	$151.41	4.105%	$157.6254	$157.63	$157.65	$157.60
Purchase #6	$45.73	5.334%	$48.1692	$48.17	$48.15	$48.20
Purchase #7	$131.98	7.327%	$141.6502	$141.65	$141.65	$141.70
7 purchase totals =	$936.86		$1,003.3546	$1,003.36	$1,003.30	$1,003.50