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	$43.66	10.139%	$48.0867	$48.09	$48.10	$48.10
Purchase #2	$244.74	6.570%	$260.8194	$260.82	$260.80	$260.80
Purchase #3	$151.98	9.171%	$165.9181	$165.92	$165.90	$165.90
Purchase #4	$116.31	11.386%	$129.5531	$129.55	$129.55	$129.60
Purchase #5	$100.38	12.227%	$112.6535	$112.65	$112.65	$112.70
Purchase #6	$213.72	4.112%	$222.5082	$222.51	$222.50	$222.50
Purchase #7	$42.59	12.244%	$47.8047	$47.80	$47.80	$47.80
7 purchase totals =	$913.38		$987.3437	$987.34	$987.30	$987.40