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	$41.38	10.483%	$45.7179	$45.72	$45.70	$45.70
Purchase #2	$200.59	7.306%	$215.2451	$215.25	$215.25	$215.20
Purchase #3	$234.27	13.742%	$266.4634	$266.46	$266.45	$266.50
Purchase #4	$63.90	13.818%	$72.7297	$72.73	$72.75	$72.70
Purchase #5	$117.34	12.465%	$131.9664	$131.97	$131.95	$132.00
Purchase #6	$243.30	8.839%	$264.8053	$264.81	$264.80	$264.80
Purchase #7	$229.40	12.348%	$257.7263	$257.73	$257.75	$257.70
7 purchase totals =	$1,130.18		$1,254.6541	$1,254.67	$1,254.65	$1,254.60