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	$14.87	7.168%	$15.9359	$15.94	$15.95	$15.90
Purchase #2	$175.49	6.189%	$186.3511	$186.35	$186.35	$186.40
Purchase #3	$42.38	4.126%	$44.1286	$44.13	$44.15	$44.10
Purchase #4	$82.77	7.838%	$89.2575	$89.26	$89.25	$89.30
Purchase #5	$143.42	4.794%	$150.2956	$150.30	$150.30	$150.30
Purchase #6	$55.60	3.412%	$57.4971	$57.50	$57.50	$57.50
Purchase #7	$142.45	5.196%	$149.8517	$149.85	$149.85	$149.90
7 purchase totals =	$656.98		$693.3175	$693.33	$693.35	$693.40