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	$205.80	8.785%	$223.8795	$223.88	$223.90	$223.90
Purchase #2	$9.85	3.525%	$10.1972	$10.20	$10.20	$10.20
Purchase #3	$64.64	11.619%	$72.1505	$72.15	$72.15	$72.20
Purchase #4	$86.64	10.125%	$95.4123	$95.41	$95.40	$95.40
Purchase #5	$191.96	10.621%	$212.3481	$212.35	$212.35	$212.30
Purchase #6	$90.52	12.230%	$101.5906	$101.59	$101.60	$101.60
Purchase #7	$146.61	6.846%	$156.6469	$156.65	$156.65	$156.60
7 purchase totals =	$796.02		$872.2251	$872.23	$872.25	$872.20