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	$87.78	11.103%	$97.5262	$97.53	$97.55	$97.50
Purchase #2	$229.51	13.629%	$260.7899	$260.79	$260.80	$260.80
Purchase #3	$156.79	7.224%	$168.1165	$168.12	$168.10	$168.10
Purchase #4	$42.69	11.874%	$47.759	$47.76	$47.75	$47.80
Purchase #5	$93.65	12.709%	$105.552	$105.55	$105.55	$105.60
Purchase #6	$80.51	6.613%	$85.8341	$85.83	$85.85	$85.80
Purchase #7	$71.60	13.341%	$81.1522	$81.15	$81.15	$81.20
7 purchase totals =	$762.53		$846.7299	$846.73	$846.75	$846.80