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	$117.29	4.819%	$122.9422	$122.94	$122.95	$122.90
Purchase #2	$134.46	6.270%	$142.8906	$142.89	$142.90	$142.90
Purchase #3	$18.29	4.754%	$19.1595	$19.16	$19.15	$19.20
Purchase #4	$82.33	13.540%	$93.4775	$93.48	$93.50	$93.50
Purchase #5	$80.71	11.454%	$89.9545	$89.95	$89.95	$90.00
Purchase #6	$218.41	11.213%	$242.9003	$242.90	$242.90	$242.90
Purchase #7	$228.43	10.271%	$251.892	$251.89	$251.90	$251.90
7 purchase totals =	$879.92		$963.2166	$963.21	$963.25	$963.30