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	$89.76	6.650%	$95.729	$95.73	$95.75	$95.70
Purchase #2	$161.53	13.845%	$183.8938	$183.89	$183.90	$183.90
Purchase #3	$75.85	3.539%	$78.5343	$78.53	$78.55	$78.50
Purchase #4	$236.46	11.540%	$263.7475	$263.75	$263.75	$263.70
Purchase #5	$213.97	6.820%	$228.5628	$228.56	$228.55	$228.60
Purchase #6	$134.55	3.763%	$139.6131	$139.61	$139.60	$139.60
Purchase #7	$138.43	12.709%	$156.0231	$156.02	$156.00	$156.00
7 purchase totals =	$1,050.55		$1,146.1036	$1,146.09	$1,146.10	$1,146.00