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	$33.39	12.834%	$37.6753	$37.68	$37.70	$37.70
Purchase #2	$42.43	10.873%	$47.0434	$47.04	$47.05	$47.00
Purchase #3	$38.38	11.262%	$42.7024	$42.70	$42.70	$42.70
Purchase #4	$134.72	11.698%	$150.4795	$150.48	$150.50	$150.50
Purchase #5	$69.97	4.321%	$72.9934	$72.99	$73.00	$73.00
Purchase #6	$240.77	7.204%	$258.1151	$258.12	$258.10	$258.10
Purchase #7	$168.86	7.489%	$181.5059	$181.51	$181.50	$181.50
7 purchase totals =	$728.52		$790.5150	$790.52	$790.55	$790.50