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	$179.28	3.399%	$185.3737	$185.37	$185.35	$185.40
Purchase #2	$147.48	3.726%	$152.9751	$152.98	$153.00	$153.00
Purchase #3	$58.84	10.684%	$65.1265	$65.13	$65.15	$65.10
Purchase #4	$194.89	7.243%	$209.0059	$209.01	$209.00	$209.00
Purchase #5	$31.47	7.152%	$33.7207	$33.72	$33.70	$33.70
Purchase #6	$35.60	6.690%	$37.9816	$37.98	$38.00	$38.00
Purchase #7	$174.38	10.363%	$192.451	$192.45	$192.45	$192.50
7 purchase totals =	$821.94		$876.6345	$876.64	$876.65	$876.70