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	$10.68	7.250%	$11.4543	$11.45	$11.45	$11.50
Purchase #2	$74.88	10.408%	$82.6735	$82.67	$82.65	$82.70
Purchase #3	$239.73	8.293%	$259.6108	$259.61	$259.60	$259.60
Purchase #4	$193.73	11.205%	$215.4374	$215.44	$215.45	$215.40
Purchase #5	$152.27	8.591%	$165.3515	$165.35	$165.35	$165.40
Purchase #6	$12.25	7.273%	$13.1409	$13.14	$13.15	$13.10
Purchase #7	$79.86	3.480%	$82.6391	$82.64	$82.65	$82.60
7 purchase totals =	$763.40		$830.3075	$830.30	$830.30	$830.30