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	$71.27	3.169%	$73.5285	$73.53	$73.55	$73.50
Purchase #2	$134.57	12.540%	$151.4451	$151.45	$151.45	$151.40
Purchase #3	$215.78	6.323%	$229.4238	$229.42	$229.40	$229.40
Purchase #4	$114.56	11.821%	$128.1021	$128.10	$128.10	$128.10
Purchase #5	$96.77	7.398%	$103.929	$103.93	$103.95	$103.90
Purchase #6	$39.54	5.210%	$41.6	$41.60	$41.60	$41.60
Purchase #7	$203.46	8.377%	$220.5038	$220.50	$220.50	$220.50
7 purchase totals =	$875.95		$948.5323	$948.53	$948.55	$948.40