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	$139.57	8.131%	$150.9184	$150.92	$150.90	$150.90
Purchase #2	$15.50	11.844%	$17.3358	$17.34	$17.35	$17.30
Purchase #3	$123.43	3.666%	$127.9549	$127.95	$127.95	$128.00
Purchase #4	$232.88	12.261%	$261.4334	$261.43	$261.45	$261.40
Purchase #5	$236.89	5.554%	$250.0469	$250.05	$250.05	$250.00
Purchase #6	$245.29	13.599%	$278.647	$278.65	$278.65	$278.60
Purchase #7	$90.69	13.713%	$103.1263	$103.13	$103.15	$103.10
7 purchase totals =	$1,084.25		$1,189.4627	$1,189.47	$1,189.50	$1,189.30