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	$32.59	7.269%	$34.959	$34.96	$34.95	$35.00
Purchase #2	$189.49	4.695%	$198.3866	$198.39	$198.40	$198.40
Purchase #3	$89.91	3.150%	$92.7422	$92.74	$92.75	$92.70
Purchase #4	$158.91	3.237%	$164.0539	$164.05	$164.05	$164.10
Purchase #5	$120.38	9.146%	$131.39	$131.39	$131.40	$131.40
Purchase #6	$110.80	3.172%	$114.3146	$114.31	$114.30	$114.30
Purchase #7	$123.58	7.348%	$132.6607	$132.66	$132.65	$132.70
7 purchase totals =	$825.66		$868.5070	$868.50	$868.50	$868.60