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	$84.60	4.680%	$88.5593	$88.56	$88.55	$88.60
Purchase #2	$57.44	10.456%	$63.4459	$63.45	$63.45	$63.40
Purchase #3	$234.78	7.403%	$252.1608	$252.16	$252.15	$252.20
Purchase #4	$226.88	13.770%	$258.1214	$258.12	$258.10	$258.10
Purchase #5	$75.53	13.317%	$85.5883	$85.59	$85.60	$85.60
Purchase #6	$183.90	3.568%	$190.4616	$190.46	$190.45	$190.50
Purchase #7	$72.98	11.427%	$81.3194	$81.32	$81.30	$81.30
7 purchase totals =	$936.11		$1,019.6567	$1,019.66	$1,019.60	$1,019.70