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	$223.43	11.730%	$249.6383	$249.64	$249.65	$249.60
Purchase #2	$23.33	11.201%	$25.9432	$25.94	$25.95	$25.90
Purchase #3	$134.72	12.707%	$151.8389	$151.84	$151.85	$151.80
Purchase #4	$99.83	3.820%	$103.6435	$103.64	$103.65	$103.60
Purchase #5	$49.94	4.822%	$52.3481	$52.35	$52.35	$52.30
Purchase #6	$156.61	6.728%	$167.1467	$167.15	$167.15	$167.10
Purchase #7	$124.47	13.637%	$141.444	$141.44	$141.45	$141.40
7 purchase totals =	$812.33		$892.0027	$892.00	$892.05	$891.70