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	$98.54	9.556%	$107.9565	$107.96	$107.95	$108.00
Purchase #2	$221.56	7.814%	$238.8727	$238.87	$238.85	$238.90
Purchase #3	$40.90	9.359%	$44.7278	$44.73	$44.75	$44.70
Purchase #4	$151.73	7.299%	$162.8048	$162.80	$162.80	$162.80
Purchase #5	$70.31	6.429%	$74.8302	$74.83	$74.85	$74.80
Purchase #6	$90.88	10.683%	$100.5887	$100.59	$100.60	$100.60
Purchase #7	$204.91	6.639%	$218.514	$218.51	$218.50	$218.50
7 purchase totals =	$878.83		$948.2947	$948.29	$948.30	$948.30