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	$142.47	11.614%	$159.0165	$159.02	$159.00	$159.00
Purchase #2	$14.33	5.686%	$15.1448	$15.14	$15.15	$15.10
Purchase #3	$31.64	3.848%	$32.8575	$32.86	$32.85	$32.90
Purchase #4	$241.49	8.580%	$262.2098	$262.21	$262.20	$262.20
Purchase #5	$33.54	11.544%	$37.4119	$37.41	$37.40	$37.40
Purchase #6	$50.63	4.871%	$53.0962	$53.10	$53.10	$53.10
Purchase #7	$143.77	9.124%	$156.8876	$156.89	$156.90	$156.90
7 purchase totals =	$657.87		$716.6243	$716.63	$716.60	$716.60