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	$184.60	6.276%	$196.1855	$196.19	$196.20	$196.20
Purchase #2	$169.77	11.135%	$188.6739	$188.67	$188.65	$188.70
Purchase #3	$116.93	4.857%	$122.6093	$122.61	$122.60	$122.60
Purchase #4	$16.59	13.734%	$18.8685	$18.87	$18.85	$18.90
Purchase #5	$72.89	7.155%	$78.1053	$78.11	$78.10	$78.10
Purchase #6	$63.38	13.554%	$71.9705	$71.97	$71.95	$72.00
Purchase #7	$168.83	12.485%	$189.9084	$189.91	$189.90	$189.90
7 purchase totals =	$792.99		$866.3214	$866.33	$866.25	$866.40