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	$116.96	11.393%	$130.2853	$130.29	$130.30	$130.30
Purchase #2	$78.50	8.502%	$85.1741	$85.17	$85.15	$85.20
Purchase #3	$43.75	4.827%	$45.8618	$45.86	$45.85	$45.90
Purchase #4	$89.76	3.280%	$92.7041	$92.70	$92.70	$92.70
Purchase #5	$225.83	4.422%	$235.8162	$235.82	$235.80	$235.80
Purchase #6	$27.79	5.859%	$29.4182	$29.42	$29.40	$29.40
Purchase #7	$163.52	4.161%	$170.3241	$170.32	$170.30	$170.30
7 purchase totals =	$746.11		$789.5838	$789.58	$789.50	$789.60