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	$97.60	7.672%	$105.0879	$105.09	$105.10	$105.10
Purchase #2	$250.31	12.462%	$281.5036	$281.50	$281.50	$281.50
Purchase #3	$79.61	12.249%	$89.3614	$89.36	$89.35	$89.40
Purchase #4	$42.80	3.117%	$44.1341	$44.13	$44.15	$44.10
Purchase #5	$183.48	12.795%	$206.9563	$206.96	$206.95	$207.00
Purchase #6	$190.52	7.397%	$204.6128	$204.61	$204.60	$204.60
Purchase #7	$153.47	7.358%	$164.7623	$164.76	$164.75	$164.80
7 purchase totals =	$997.79		$1,096.4184	$1,096.41	$1,096.40	$1,096.50