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	$114.46	11.413%	$127.5233	$127.52	$127.50	$127.50
Purchase #2	$191.52	12.104%	$214.7016	$214.70	$214.70	$214.70
Purchase #3	$72.29	12.558%	$81.3682	$81.37	$81.35	$81.40
Purchase #4	$221.91	10.386%	$244.9576	$244.96	$244.95	$245.00
Purchase #5	$79.26	3.650%	$82.153	$82.15	$82.15	$82.20
Purchase #6	$166.26	8.381%	$180.1943	$180.19	$180.20	$180.20
Purchase #7	$104.70	4.658%	$109.5769	$109.58	$109.60	$109.60
7 purchase totals =	$950.40		$1,040.4749	$1,040.47	$1,040.45	$1,040.60