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	$216.67	3.163%	$223.5233	$223.52	$223.50	$223.50
Purchase #2	$110.59	3.181%	$114.1079	$114.11	$114.10	$114.10
Purchase #3	$189.92	9.713%	$208.3669	$208.37	$208.35	$208.40
Purchase #4	$96.52	12.126%	$108.224	$108.22	$108.20	$108.20
Purchase #5	$71.63	11.454%	$79.8345	$79.83	$79.85	$79.80
Purchase #6	$142.97	11.111%	$158.8554	$158.86	$158.85	$158.90
Purchase #7	$86.66	9.162%	$94.5998	$94.60	$94.60	$94.60
7 purchase totals =	$914.96		$987.5118	$987.51	$987.45	$987.50