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	$101.38	11.765%	$113.3074	$113.31	$113.30	$113.30
Purchase #2	$51.80	3.549%	$53.6384	$53.64	$53.65	$53.60
Purchase #3	$232.45	7.615%	$250.1511	$250.15	$250.15	$250.20
Purchase #4	$49.57	5.559%	$52.3256	$52.33	$52.35	$52.30
Purchase #5	$238.72	7.416%	$256.4235	$256.42	$256.40	$256.40
Purchase #6	$186.89	12.157%	$209.6102	$209.61	$209.60	$209.60
Purchase #7	$138.54	11.303%	$154.1992	$154.20	$154.20	$154.20
7 purchase totals =	$999.35		$1,089.6554	$1,089.66	$1,089.65	$1,089.60