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	$150.68	3.542%	$156.0171	$156.02	$156.00	$156.00
Purchase #2	$31.25	3.203%	$32.2509	$32.25	$32.25	$32.30
Purchase #3	$204.47	9.145%	$223.1688	$223.17	$223.15	$223.20
Purchase #4	$117.59	3.318%	$121.4916	$121.49	$121.50	$121.50
Purchase #5	$217.83	7.672%	$234.5419	$234.54	$234.55	$234.50
Purchase #6	$212.74	12.305%	$238.9177	$238.92	$238.90	$238.90
Purchase #7	$71.98	8.786%	$78.3042	$78.30	$78.30	$78.30
7 purchase totals =	$1,006.54		$1,084.6922	$1,084.69	$1,084.65	$1,084.70