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	$235.55	13.679%	$267.7709	$267.77	$267.75	$267.80
Purchase #2	$93.28	7.397%	$100.1799	$100.18	$100.20	$100.20
Purchase #3	$80.30	12.410%	$90.2652	$90.27	$90.25	$90.30
Purchase #4	$91.29	6.863%	$97.5552	$97.56	$97.55	$97.60
Purchase #5	$86.64	12.515%	$97.483	$97.48	$97.50	$97.50
Purchase #6	$134.62	12.581%	$151.5565	$151.56	$151.55	$151.60
Purchase #7	$60.92	9.117%	$66.4741	$66.47	$66.45	$66.50
7 purchase totals =	$782.60		$871.2848	$871.29	$871.25	$871.50