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	$87.58	12.323%	$98.3725	$98.37	$98.35	$98.40
Purchase #2	$79.42	13.213%	$89.9138	$89.91	$89.90	$89.90
Purchase #3	$6.27	12.597%	$7.0598	$7.06	$7.05	$7.10
Purchase #4	$233.54	13.530%	$265.138	$265.14	$265.15	$265.10
Purchase #5	$34.75	10.851%	$38.5207	$38.52	$38.50	$38.50
Purchase #6	$201.87	12.261%	$226.6213	$226.62	$226.60	$226.60
Purchase #7	$80.90	5.552%	$85.3916	$85.39	$85.40	$85.40
7 purchase totals =	$724.33		$811.0177	$811.01	$810.95	$811.00