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	$250.73	4.744%	$262.6246	$262.62	$262.60	$262.60
Purchase #2	$156.83	11.468%	$174.8153	$174.82	$174.80	$174.80
Purchase #3	$25.98	13.554%	$29.5013	$29.50	$29.50	$29.50
Purchase #4	$219.91	13.807%	$250.273	$250.27	$250.25	$250.30
Purchase #5	$57.42	9.606%	$62.9358	$62.94	$62.95	$62.90
Purchase #6	$76.77	5.848%	$81.2595	$81.26	$81.25	$81.30
Purchase #7	$219.89	6.798%	$234.8381	$234.84	$234.85	$234.80
7 purchase totals =	$1,007.53		$1,096.2476	$1,096.25	$1,096.20	$1,096.20