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	$62.63	4.629%	$65.5291	$65.53	$65.55	$65.50
Purchase #2	$151.56	10.523%	$167.5087	$167.51	$167.50	$167.50
Purchase #3	$25.63	6.371%	$27.2629	$27.26	$27.25	$27.30
Purchase #4	$27.65	5.706%	$29.2277	$29.23	$29.25	$29.20
Purchase #5	$200.89	11.191%	$223.3716	$223.37	$223.35	$223.40
Purchase #6	$53.37	4.224%	$55.6243	$55.62	$55.60	$55.60
Purchase #7	$136.60	6.699%	$145.7508	$145.75	$145.75	$145.80
7 purchase totals =	$658.33		$714.2751	$714.27	$714.25	$714.30