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	$127.44	11.489%	$142.0816	$142.08	$142.10	$142.10
Purchase #2	$195.31	5.550%	$206.1497	$206.15	$206.15	$206.10
Purchase #3	$82.57	5.672%	$87.2534	$87.25	$87.25	$87.30
Purchase #4	$240.92	12.687%	$271.4855	$271.49	$271.50	$271.50
Purchase #5	$29.60	11.195%	$32.9137	$32.91	$32.90	$32.90
Purchase #6	$83.76	7.703%	$90.212	$90.21	$90.20	$90.20
Purchase #7	$171.73	9.783%	$188.5303	$188.53	$188.55	$188.50
7 purchase totals =	$931.33		$1,018.6262	$1,018.62	$1,018.65	$1,018.60