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	$73.87	12.374%	$83.0107	$83.01	$83.00	$83.00
Purchase #2	$144.78	7.305%	$155.3562	$155.36	$155.35	$155.40
Purchase #3	$174.52	12.390%	$196.143	$196.14	$196.15	$196.10
Purchase #4	$185.69	13.102%	$210.0191	$210.02	$210.00	$210.00
Purchase #5	$97.87	12.858%	$110.4541	$110.45	$110.45	$110.50
Purchase #6	$199.45	7.752%	$214.9114	$214.91	$214.90	$214.90
Purchase #7	$160.88	7.234%	$172.5181	$172.52	$172.50	$172.50
7 purchase totals =	$1,037.06		$1,142.4126	$1,142.41	$1,142.35	$1,142.40