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	$31.75	10.476%	$35.0761	$35.08	$35.10	$35.10
Purchase #2	$56.37	4.666%	$59.0002	$59.00	$59.00	$59.00
Purchase #3	$156.44	5.507%	$165.0552	$165.06	$165.05	$165.10
Purchase #4	$65.40	3.750%	$67.8525	$67.85	$67.85	$67.90
Purchase #5	$215.25	13.675%	$244.6854	$244.69	$244.70	$244.70
Purchase #6	$138.82	13.649%	$157.7675	$157.77	$157.75	$157.80
Purchase #7	$238.69	12.806%	$269.2566	$269.26	$269.25	$269.30
7 purchase totals =	$902.72		$998.6935	$998.71	$998.70	$998.90