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	$159.84	13.455%	$181.3465	$181.35	$181.35	$181.30
Purchase #2	$168.50	13.554%	$191.3385	$191.34	$191.35	$191.30
Purchase #3	$187.39	10.149%	$206.4082	$206.41	$206.40	$206.40
Purchase #4	$113.91	12.447%	$128.0884	$128.09	$128.10	$128.10
Purchase #5	$103.61	7.204%	$111.0741	$111.07	$111.05	$111.10
Purchase #6	$98.77	13.372%	$111.9775	$111.98	$112.00	$112.00
Purchase #7	$237.71	13.275%	$269.266	$269.27	$269.25	$269.30
7 purchase totals =	$1,069.73		$1,199.4992	$1,199.51	$1,199.50	$1,199.50