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	$238.70	4.270%	$248.8925	$248.89	$248.90	$248.90
Purchase #2	$12.30	6.161%	$13.0578	$13.06	$13.05	$13.10
Purchase #3	$64.28	13.825%	$73.1667	$73.17	$73.15	$73.20
Purchase #4	$26.28	4.639%	$27.4991	$27.50	$27.50	$27.50
Purchase #5	$94.83	11.574%	$105.8056	$105.81	$105.80	$105.80
Purchase #6	$222.59	7.228%	$238.6788	$238.68	$238.70	$238.70
Purchase #7	$24.58	4.179%	$25.6072	$25.61	$25.60	$25.60
7 purchase totals =	$683.56		$732.7077	$732.72	$732.70	$732.80