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	$54.84	12.795%	$61.8568	$61.86	$61.85	$61.90
Purchase #2	$238.85	12.483%	$268.6656	$268.67	$268.65	$268.70
Purchase #3	$31.59	11.258%	$35.1464	$35.15	$35.15	$35.10
Purchase #4	$31.25	13.308%	$35.4088	$35.41	$35.40	$35.40
Purchase #5	$244.50	4.853%	$256.3656	$256.37	$256.35	$256.40
Purchase #6	$130.55	6.276%	$138.7433	$138.74	$138.75	$138.70
Purchase #7	$217.96	10.117%	$240.011	$240.01	$240.00	$240.00
7 purchase totals =	$949.54		$1,036.1975	$1,036.21	$1,036.15	$1,036.20