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	$40.58	6.541%	$43.2343	$43.23	$43.25	$43.20
Purchase #2	$219.33	3.145%	$226.2279	$226.23	$226.25	$226.20
Purchase #3	$198.54	12.503%	$223.3635	$223.36	$223.35	$223.40
Purchase #4	$169.43	12.582%	$190.7477	$190.75	$190.75	$190.70
Purchase #5	$43.94	11.749%	$49.1025	$49.10	$49.10	$49.10
Purchase #6	$214.69	12.668%	$241.8869	$241.89	$241.90	$241.90
Purchase #7	$116.38	6.246%	$123.6491	$123.65	$123.65	$123.60
7 purchase totals =	$1,002.89		$1,098.2119	$1,098.21	$1,098.25	$1,098.10