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	$108.96	13.612%	$123.7916	$123.79	$123.80	$123.80
Purchase #2	$32.59	7.744%	$35.1138	$35.11	$35.10	$35.10
Purchase #3	$193.40	3.237%	$199.6604	$199.66	$199.65	$199.70
Purchase #4	$106.95	6.745%	$114.1638	$114.16	$114.15	$114.20
Purchase #5	$210.89	4.561%	$220.5087	$220.51	$220.50	$220.50
Purchase #6	$182.33	5.314%	$192.019	$192.02	$192.00	$192.00
Purchase #7	$183.62	9.266%	$200.6342	$200.63	$200.65	$200.60
7 purchase totals =	$1,018.74		$1,085.8915	$1,085.88	$1,085.85	$1,085.90