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	$186.84	5.224%	$196.6005	$196.60	$196.60	$196.60
Purchase #2	$71.66	11.564%	$79.9468	$79.95	$79.95	$79.90
Purchase #3	$58.91	10.259%	$64.9536	$64.95	$64.95	$65.00
Purchase #4	$249.25	5.208%	$262.2309	$262.23	$262.25	$262.20
Purchase #5	$180.68	5.451%	$190.5289	$190.53	$190.55	$190.50
Purchase #6	$15.84	13.662%	$18.0041	$18.00	$18.00	$18.00
Purchase #7	$98.32	13.783%	$111.8714	$111.87	$111.85	$111.90
7 purchase totals =	$861.50		$924.1362	$924.13	$924.15	$924.10