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	$78.91	9.223%	$86.1879	$86.19	$86.20	$86.20
Purchase #2	$196.96	10.402%	$217.4478	$217.45	$217.45	$217.40
Purchase #3	$147.90	9.459%	$161.8899	$161.89	$161.90	$161.90
Purchase #4	$171.84	7.297%	$184.3792	$184.38	$184.40	$184.40
Purchase #5	$211.48	8.480%	$229.4135	$229.41	$229.40	$229.40
Purchase #6	$188.29	4.321%	$196.426	$196.43	$196.45	$196.40
Purchase #7	$156.28	10.874%	$173.2739	$173.27	$173.25	$173.30
7 purchase totals =	$1,151.66		$1,249.0182	$1,249.02	$1,249.05	$1,249.00