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	$122.82	3.633%	$127.2821	$127.28	$127.30	$127.30
Purchase #2	$40.31	5.507%	$42.5299	$42.53	$42.55	$42.50
Purchase #3	$69.82	3.222%	$72.0696	$72.07	$72.05	$72.10
Purchase #4	$95.68	3.739%	$99.2575	$99.26	$99.25	$99.30
Purchase #5	$24.86	6.841%	$26.5607	$26.56	$26.55	$26.60
Purchase #6	$177.34	4.835%	$185.9144	$185.91	$185.90	$185.90
Purchase #7	$160.46	4.718%	$168.0305	$168.03	$168.05	$168.00
7 purchase totals =	$691.29		$721.6447	$721.64	$721.65	$721.70