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	$158.88	10.154%	$175.0127	$175.01	$175.00	$175.00
Purchase #2	$67.55	12.839%	$76.2227	$76.22	$76.20	$76.20
Purchase #3	$212.74	4.526%	$222.3686	$222.37	$222.35	$222.40
Purchase #4	$131.30	8.698%	$142.7205	$142.72	$142.70	$142.70
Purchase #5	$31.80	5.215%	$33.4584	$33.46	$33.45	$33.50
Purchase #6	$66.47	6.684%	$70.9129	$70.91	$70.90	$70.90
Purchase #7	$77.37	10.325%	$85.3585	$85.36	$85.35	$85.40
7 purchase totals =	$746.11		$806.0543	$806.05	$805.95	$806.10