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	$195.63	4.541%	$204.5136	$204.51	$204.50	$204.50
Purchase #2	$197.69	11.627%	$220.6754	$220.68	$220.70	$220.70
Purchase #3	$172.61	10.545%	$190.8117	$190.81	$190.80	$190.80
Purchase #4	$37.85	11.614%	$42.2459	$42.25	$42.25	$42.20
Purchase #5	$179.93	6.464%	$191.5607	$191.56	$191.55	$191.60
Purchase #6	$218.71	13.663%	$248.5923	$248.59	$248.60	$248.60
Purchase #7	$139.59	3.703%	$144.759	$144.76	$144.75	$144.80
7 purchase totals =	$1,142.01		$1,243.1586	$1,243.16	$1,243.15	$1,243.20