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	$28.86	13.533%	$32.7656	$32.77	$32.75	$32.80
Purchase #2	$110.72	8.827%	$120.4933	$120.49	$120.50	$120.50
Purchase #3	$13.93	11.638%	$15.5512	$15.55	$15.55	$15.60
Purchase #4	$162.93	6.551%	$173.6035	$173.60	$173.60	$173.60
Purchase #5	$39.90	6.485%	$42.4875	$42.49	$42.50	$42.50
Purchase #6	$69.29	6.753%	$73.9692	$73.97	$73.95	$74.00
Purchase #7	$200.38	11.412%	$223.2474	$223.25	$223.25	$223.20
7 purchase totals =	$626.01		$682.1177	$682.12	$682.10	$682.20