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	$176.71	7.732%	$190.3732	$190.37	$190.35	$190.40
Purchase #2	$181.60	5.499%	$191.5862	$191.59	$191.60	$191.60
Purchase #3	$104.64	9.243%	$114.3119	$114.31	$114.30	$114.30
Purchase #4	$108.93	7.376%	$116.9647	$116.96	$116.95	$117.00
Purchase #5	$16.36	7.113%	$17.5237	$17.52	$17.50	$17.50
Purchase #6	$45.59	10.272%	$50.273	$50.27	$50.25	$50.30
Purchase #7	$63.50	13.597%	$72.1341	$72.13	$72.15	$72.10
7 purchase totals =	$697.33		$753.1668	$753.15	$753.10	$753.20