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	$124.83	4.157%	$130.0192	$130.02	$130.00	$130.00
Purchase #2	$169.62	6.693%	$180.9727	$180.97	$180.95	$181.00
Purchase #3	$35.25	9.110%	$38.4613	$38.46	$38.45	$38.50
Purchase #4	$211.94	10.137%	$233.4244	$233.42	$233.40	$233.40
Purchase #5	$62.62	5.568%	$66.1067	$66.11	$66.10	$66.10
Purchase #6	$90.36	9.659%	$99.0879	$99.09	$99.10	$99.10
Purchase #7	$142.78	11.232%	$158.817	$158.82	$158.80	$158.80
7 purchase totals =	$837.40		$906.8892	$906.89	$906.80	$906.90