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	$181.56	5.455%	$191.4641	$191.46	$191.45	$191.50
Purchase #2	$221.92	13.631%	$252.1699	$252.17	$252.15	$252.20
Purchase #3	$113.74	5.363%	$119.8399	$119.84	$119.85	$119.80
Purchase #4	$212.70	4.719%	$222.7373	$222.74	$222.75	$222.70
Purchase #5	$5.93	7.328%	$6.3646	$6.36	$6.35	$6.40
Purchase #6	$126.37	10.404%	$139.5175	$139.52	$139.50	$139.50
Purchase #7	$142.34	8.485%	$154.4175	$154.42	$154.40	$154.40
7 purchase totals =	$1,004.56		$1,086.5108	$1,086.51	$1,086.45	$1,086.50