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	$222.29	10.639%	$245.9394	$245.94	$245.95	$245.90
Purchase #2	$74.62	10.517%	$82.4678	$82.47	$82.45	$82.50
Purchase #3	$67.80	7.188%	$72.6735	$72.67	$72.65	$72.70
Purchase #4	$161.37	12.873%	$182.1432	$182.14	$182.15	$182.10
Purchase #5	$45.50	7.757%	$49.0294	$49.03	$49.05	$49.00
Purchase #6	$45.57	5.608%	$48.1256	$48.13	$48.15	$48.10
Purchase #7	$186.54	13.592%	$211.8945	$211.89	$211.90	$211.90
7 purchase totals =	$803.69		$892.2734	$892.27	$892.30	$892.20