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	$179.41	4.343%	$187.2018	$187.20	$187.20	$187.20
Purchase #2	$40.85	7.787%	$44.031	$44.03	$44.05	$44.00
Purchase #3	$128.76	10.463%	$142.2322	$142.23	$142.25	$142.20
Purchase #4	$12.27	10.191%	$13.5204	$13.52	$13.50	$13.50
Purchase #5	$103.80	10.618%	$114.8215	$114.82	$114.80	$114.80
Purchase #6	$241.42	11.473%	$269.1181	$269.12	$269.10	$269.10
Purchase #7	$221.81	8.411%	$240.4664	$240.47	$240.45	$240.50
7 purchase totals =	$928.32		$1,011.3914	$1,011.39	$1,011.35	$1,011.30