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	$155.99	3.859%	$162.0097	$162.01	$162.00	$162.00
Purchase #2	$142.95	5.794%	$151.2325	$151.23	$151.25	$151.20
Purchase #3	$229.57	6.672%	$244.8869	$244.89	$244.90	$244.90
Purchase #4	$32.79	7.554%	$35.267	$35.27	$35.25	$35.30
Purchase #5	$138.26	10.423%	$152.6708	$152.67	$152.65	$152.70
Purchase #6	$225.74	7.127%	$241.8285	$241.83	$241.85	$241.80
Purchase #7	$150.71	11.364%	$167.8367	$167.84	$167.85	$167.80
7 purchase totals =	$1,076.01		$1,155.7321	$1,155.74	$1,155.75	$1,155.70