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	$63.63	13.685%	$72.3378	$72.34	$72.35	$72.30
Purchase #2	$44.66	9.821%	$49.0461	$49.05	$49.05	$49.00
Purchase #3	$30.29	11.779%	$33.8579	$33.86	$33.85	$33.90
Purchase #4	$78.98	5.603%	$83.4052	$83.41	$83.40	$83.40
Purchase #5	$167.69	4.701%	$175.5731	$175.57	$175.55	$175.60
Purchase #6	$201.78	6.856%	$215.614	$215.61	$215.60	$215.60
Purchase #7	$218.75	6.642%	$233.2794	$233.28	$233.30	$233.30
7 purchase totals =	$805.78		$863.1135	$863.12	$863.10	$863.10