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	$126.61	10.129%	$139.4343	$139.43	$139.45	$139.40
Purchase #2	$127.55	6.128%	$135.3663	$135.37	$135.35	$135.40
Purchase #3	$205.29	5.689%	$216.9689	$216.97	$216.95	$217.00
Purchase #4	$223.90	4.413%	$233.7807	$233.78	$233.80	$233.80
Purchase #5	$159.61	5.516%	$168.4141	$168.41	$168.40	$168.40
Purchase #6	$57.73	11.635%	$64.4469	$64.45	$64.45	$64.40
Purchase #7	$126.45	12.330%	$142.0413	$142.04	$142.05	$142.00
7 purchase totals =	$1,027.14		$1,100.4525	$1,100.45	$1,100.45	$1,100.40