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	$107.36	6.747%	$114.6036	$114.60	$114.60	$114.60
Purchase #2	$116.96	9.321%	$127.8618	$127.86	$127.85	$127.90
Purchase #3	$100.88	5.123%	$106.0481	$106.05	$106.05	$106.00
Purchase #4	$127.77	11.600%	$142.5913	$142.59	$142.60	$142.60
Purchase #5	$196.43	9.412%	$214.918	$214.92	$214.90	$214.90
Purchase #6	$115.70	8.867%	$125.9591	$125.96	$125.95	$126.00
Purchase #7	$130.66	8.600%	$141.8968	$141.90	$141.90	$141.90
7 purchase totals =	$895.76		$973.8787	$973.88	$973.85	$973.90