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	$32.28	9.102%	$35.2181	$35.22	$35.20	$35.20
Purchase #2	$50.48	8.749%	$54.8965	$54.90	$54.90	$54.90
Purchase #3	$33.48	13.118%	$37.8719	$37.87	$37.85	$37.90
Purchase #4	$229.67	9.204%	$250.8088	$250.81	$250.80	$250.80
Purchase #5	$134.60	3.277%	$139.0108	$139.01	$139.00	$139.00
Purchase #6	$38.81	11.820%	$43.3973	$43.40	$43.40	$43.40
Purchase #7	$196.34	4.335%	$204.8513	$204.85	$204.85	$204.90
7 purchase totals =	$715.66		$766.0547	$766.06	$766.00	$766.10