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	$209.34	3.123%	$215.8777	$215.88	$215.90	$215.90
Purchase #2	$186.64	13.138%	$211.1608	$211.16	$211.15	$211.20
Purchase #3	$112.64	9.531%	$123.3757	$123.38	$123.40	$123.40
Purchase #4	$65.67	5.751%	$69.4467	$69.45	$69.45	$69.40
Purchase #5	$59.96	9.306%	$65.5399	$65.54	$65.55	$65.50
Purchase #6	$6.34	10.550%	$7.0089	$7.01	$7.00	$7.00
Purchase #7	$87.64	10.717%	$97.0324	$97.03	$97.05	$97.00
7 purchase totals =	$728.23		$789.4421	$789.45	$789.50	$789.40