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	$193.59	6.540%	$206.2508	$206.25	$206.25	$206.30
Purchase #2	$121.71	8.379%	$131.9081	$131.91	$131.90	$131.90
Purchase #3	$130.61	12.627%	$147.1021	$147.10	$147.10	$147.10
Purchase #4	$28.83	12.753%	$32.5067	$32.51	$32.50	$32.50
Purchase #5	$210.65	4.230%	$219.5605	$219.56	$219.55	$219.60
Purchase #6	$136.31	12.872%	$153.8558	$153.86	$153.85	$153.90
Purchase #7	$223.72	8.342%	$242.3827	$242.38	$242.40	$242.40
7 purchase totals =	$1,045.42		$1,133.5667	$1,133.57	$1,133.55	$1,133.70