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	$176.53	5.547%	$186.3221	$186.32	$186.30	$186.30
Purchase #2	$189.40	3.812%	$196.6199	$196.62	$196.60	$196.60
Purchase #3	$7.61	4.571%	$7.9579	$7.96	$7.95	$8.00
Purchase #4	$111.58	10.319%	$123.0939	$123.09	$123.10	$123.10
Purchase #5	$114.92	13.635%	$130.5893	$130.59	$130.60	$130.60
Purchase #6	$105.71	4.491%	$110.4574	$110.46	$110.45	$110.50
Purchase #7	$222.35	10.135%	$244.8852	$244.89	$244.90	$244.90
7 purchase totals =	$928.10		$999.9257	$999.93	$999.90	$1,000.00