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	$60.71	10.485%	$67.0754	$67.08	$67.10	$67.10
Purchase #2	$33.57	11.241%	$37.3436	$37.34	$37.35	$37.30
Purchase #3	$12.36	5.708%	$13.0655	$13.07	$13.05	$13.10
Purchase #4	$73.73	5.177%	$77.547	$77.55	$77.55	$77.50
Purchase #5	$65.71	13.181%	$74.3712	$74.37	$74.35	$74.40
Purchase #6	$200.27	8.136%	$216.564	$216.56	$216.55	$216.60
Purchase #7	$181.31	8.593%	$196.89	$196.89	$196.90	$196.90
7 purchase totals =	$627.66		$682.8567	$682.86	$682.85	$682.90