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	$63.33	4.412%	$66.1241	$66.12	$66.10	$66.10
Purchase #2	$124.99	3.655%	$129.5584	$129.56	$129.55	$129.60
Purchase #3	$160.25	7.567%	$172.3761	$172.38	$172.40	$172.40
Purchase #4	$100.33	11.651%	$112.0194	$112.02	$112.00	$112.00
Purchase #5	$221.91	3.152%	$228.9046	$228.90	$228.90	$228.90
Purchase #6	$138.60	11.323%	$154.2937	$154.29	$154.30	$154.30
Purchase #7	$177.79	11.699%	$198.5897	$198.59	$198.60	$198.60
7 purchase totals =	$987.20		$1,061.8660	$1,061.86	$1,061.85	$1,061.90