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	$177.54	5.351%	$187.0402	$187.04	$187.05	$187.00
Purchase #2	$221.60	11.591%	$247.2857	$247.29	$247.30	$247.30
Purchase #3	$72.84	7.306%	$78.1617	$78.16	$78.15	$78.20
Purchase #4	$90.35	4.632%	$94.535	$94.54	$94.55	$94.50
Purchase #5	$32.86	7.854%	$35.4408	$35.44	$35.45	$35.40
Purchase #6	$188.74	6.451%	$200.9156	$200.92	$200.90	$200.90
Purchase #7	$109.90	11.550%	$122.5935	$122.59	$122.60	$122.60
7 purchase totals =	$893.83		$965.9725	$965.98	$966.00	$965.90