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	$37.73	4.800%	$39.541	$39.54	$39.55	$39.50
Purchase #2	$81.60	7.403%	$87.6408	$87.64	$87.65	$87.60
Purchase #3	$169.60	10.223%	$186.9382	$186.94	$186.95	$186.90
Purchase #4	$84.29	4.708%	$88.2584	$88.26	$88.25	$88.30
Purchase #5	$192.79	11.689%	$215.3252	$215.33	$215.35	$215.30
Purchase #6	$105.53	5.801%	$111.6518	$111.65	$111.65	$111.70
Purchase #7	$63.51	6.134%	$67.4057	$67.41	$67.40	$67.40
7 purchase totals =	$735.05		$796.7611	$796.77	$796.80	$796.70