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	$36.51	12.404%	$41.0387	$41.04	$41.05	$41.00
Purchase #2	$68.26	6.174%	$72.4744	$72.47	$72.45	$72.50
Purchase #3	$87.61	7.345%	$94.045	$94.05	$94.05	$94.00
Purchase #4	$49.59	11.806%	$55.4446	$55.44	$55.45	$55.40
Purchase #5	$12.59	12.377%	$14.1483	$14.15	$14.15	$14.10
Purchase #6	$103.88	10.259%	$114.537	$114.54	$114.55	$114.50
Purchase #7	$123.85	6.391%	$131.7653	$131.77	$131.75	$131.80
7 purchase totals =	$482.29		$523.4533	$523.46	$523.45	$523.30