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	$106.83	9.642%	$117.1305	$117.13	$117.15	$117.10
Purchase #2	$89.56	10.801%	$99.2334	$99.23	$99.25	$99.20
Purchase #3	$140.34	5.420%	$147.9464	$147.95	$147.95	$147.90
Purchase #4	$32.32	5.666%	$34.1513	$34.15	$34.15	$34.20
Purchase #5	$182.54	9.647%	$200.1496	$200.15	$200.15	$200.10
Purchase #6	$79.37	4.316%	$82.7956	$82.80	$82.80	$82.80
Purchase #7	$39.30	11.105%	$43.6643	$43.66	$43.65	$43.70
7 purchase totals =	$670.26		$725.0711	$725.07	$725.10	$725.00