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	$19.28	12.151%	$21.6227	$21.62	$21.60	$21.60
Purchase #2	$32.84	8.144%	$35.5145	$35.51	$35.50	$35.50
Purchase #3	$6.88	7.647%	$7.4061	$7.41	$7.40	$7.40
Purchase #4	$104.79	12.299%	$117.6781	$117.68	$117.70	$117.70
Purchase #5	$11.33	5.281%	$11.9283	$11.93	$11.95	$11.90
Purchase #6	$172.73	13.778%	$196.5287	$196.53	$196.55	$196.50
Purchase #7	$71.49	9.556%	$78.3216	$78.32	$78.30	$78.30
7 purchase totals =	$419.34		$469.0000	$469.00	$469.00	$468.90