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	$240.99	10.458%	$266.1927	$266.19	$266.20	$266.20
Purchase #2	$41.50	3.526%	$42.9633	$42.96	$42.95	$43.00
Purchase #3	$152.70	10.830%	$169.2374	$169.24	$169.25	$169.20
Purchase #4	$89.85	11.784%	$100.4379	$100.44	$100.45	$100.40
Purchase #5	$78.30	5.510%	$82.6143	$82.61	$82.60	$82.60
Purchase #6	$116.41	11.739%	$130.0754	$130.08	$130.10	$130.10
Purchase #7	$85.80	10.719%	$94.9969	$95.00	$95.00	$95.00
7 purchase totals =	$805.55		$886.5179	$886.52	$886.55	$886.50