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	$74.80	7.441%	$80.3659	$80.37	$80.35	$80.40
Purchase #2	$154.54	7.637%	$166.3422	$166.34	$166.35	$166.30
Purchase #3	$186.88	13.113%	$211.3856	$211.39	$211.40	$211.40
Purchase #4	$47.82	10.113%	$52.656	$52.66	$52.65	$52.70
Purchase #5	$150.77	11.828%	$168.6031	$168.60	$168.60	$168.60
Purchase #6	$195.32	6.563%	$208.1389	$208.14	$208.15	$208.10
Purchase #7	$113.80	5.293%	$119.8234	$119.82	$119.80	$119.80
7 purchase totals =	$923.93		$1,007.3151	$1,007.32	$1,007.30	$1,007.30