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	$88.30	3.691%	$91.5592	$91.56	$91.55	$91.60
Purchase #2	$171.92	10.431%	$189.853	$189.85	$189.85	$189.90
Purchase #3	$14.69	6.127%	$15.5901	$15.59	$15.60	$15.60
Purchase #4	$131.97	9.593%	$144.6299	$144.63	$144.65	$144.60
Purchase #5	$37.86	10.572%	$41.8626	$41.86	$41.85	$41.90
Purchase #6	$226.47	12.338%	$254.4119	$254.41	$254.40	$254.40
Purchase #7	$164.28	5.147%	$172.7355	$172.74	$172.75	$172.70
7 purchase totals =	$835.49		$910.6422	$910.64	$910.65	$910.70