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	$170.32	8.652%	$185.0561	$185.06	$185.05	$185.10
Purchase #2	$12.42	6.262%	$13.1977	$13.20	$13.20	$13.20
Purchase #3	$213.37	4.337%	$222.6239	$222.62	$222.60	$222.60
Purchase #4	$135.85	12.321%	$152.5881	$152.59	$152.60	$152.60
Purchase #5	$238.50	4.417%	$249.0345	$249.03	$249.05	$249.00
Purchase #6	$86.25	13.759%	$98.1171	$98.12	$98.10	$98.10
Purchase #7	$208.32	6.873%	$222.6378	$222.64	$222.65	$222.60
7 purchase totals =	$1,065.03		$1,143.2552	$1,143.26	$1,143.25	$1,143.20