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	$211.90	5.413%	$223.3701	$223.37	$223.35	$223.40
Purchase #2	$148.45	8.181%	$160.5947	$160.59	$160.60	$160.60
Purchase #3	$45.99	11.667%	$51.3557	$51.36	$51.35	$51.40
Purchase #4	$110.29	7.586%	$118.6566	$118.66	$118.65	$118.70
Purchase #5	$45.78	4.794%	$47.9747	$47.97	$47.95	$48.00
Purchase #6	$185.49	13.358%	$210.2678	$210.27	$210.25	$210.30
Purchase #7	$65.59	10.454%	$72.4468	$72.45	$72.45	$72.40
7 purchase totals =	$813.49		$884.6664	$884.67	$884.60	$884.80