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	$157.67	13.578%	$179.0784	$179.08	$179.10	$179.10
Purchase #2	$43.70	4.639%	$45.7272	$45.73	$45.75	$45.70
Purchase #3	$202.33	12.269%	$227.1539	$227.15	$227.15	$227.20
Purchase #4	$245.85	6.706%	$262.3367	$262.34	$262.35	$262.30
Purchase #5	$214.68	3.830%	$222.9022	$222.90	$222.90	$222.90
Purchase #6	$105.87	6.234%	$112.4699	$112.47	$112.45	$112.50
Purchase #7	$34.91	6.722%	$37.2567	$37.26	$37.25	$37.30
7 purchase totals =	$1,005.01		$1,086.9250	$1,086.93	$1,086.95	$1,087.00