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	$222.78	7.122%	$238.6464	$238.65	$238.65	$238.60
Purchase #2	$241.78	9.586%	$264.957	$264.96	$264.95	$265.00
Purchase #3	$94.84	11.539%	$105.7836	$105.78	$105.80	$105.80
Purchase #4	$160.93	6.210%	$170.9238	$170.92	$170.90	$170.90
Purchase #5	$185.43	7.591%	$199.506	$199.51	$199.50	$199.50
Purchase #6	$99.64	3.452%	$103.0796	$103.08	$103.10	$103.10
Purchase #7	$158.54	3.707%	$164.4171	$164.42	$164.40	$164.40
7 purchase totals =	$1,163.94		$1,247.3135	$1,247.32	$1,247.30	$1,247.30