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	$161.33	4.432%	$168.4801	$168.48	$168.50	$168.50
Purchase #2	$10.89	9.316%	$11.9045	$11.90	$11.90	$11.90
Purchase #3	$230.41	10.138%	$253.769	$253.77	$253.75	$253.80
Purchase #4	$178.98	7.285%	$192.0187	$192.02	$192.00	$192.00
Purchase #5	$7.57	4.749%	$7.9295	$7.93	$7.95	$7.90
Purchase #6	$118.69	7.678%	$127.803	$127.80	$127.80	$127.80
Purchase #7	$17.93	5.765%	$18.9637	$18.96	$18.95	$19.00
7 purchase totals =	$725.80		$780.8685	$780.86	$780.85	$780.90