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	$13.88	5.231%	$14.6061	$14.61	$14.60	$14.60
Purchase #2	$140.59	11.579%	$156.8689	$156.87	$156.85	$156.90
Purchase #3	$120.31	5.652%	$127.1099	$127.11	$127.10	$127.10
Purchase #4	$224.78	11.461%	$250.542	$250.54	$250.55	$250.50
Purchase #5	$103.44	11.187%	$115.0118	$115.01	$115.00	$115.00
Purchase #6	$133.73	7.515%	$143.7798	$143.78	$143.80	$143.80
Purchase #7	$245.74	13.336%	$278.5119	$278.51	$278.50	$278.50
7 purchase totals =	$982.47		$1,086.4304	$1,086.43	$1,086.40	$1,086.40