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	$102.33	8.770%	$111.3043	$111.30	$111.30	$111.30
Purchase #2	$17.91	7.703%	$19.2896	$19.29	$19.30	$19.30
Purchase #3	$83.80	7.709%	$90.2601	$90.26	$90.25	$90.30
Purchase #4	$115.86	13.533%	$131.5393	$131.54	$131.55	$131.50
Purchase #5	$181.85	7.563%	$195.6033	$195.60	$195.60	$195.60
Purchase #6	$207.28	4.608%	$216.8315	$216.83	$216.85	$216.80
Purchase #7	$36.96	6.334%	$39.301	$39.30	$39.30	$39.30
7 purchase totals =	$745.99		$804.1291	$804.12	$804.15	$804.10