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	$127.62	12.317%	$143.339	$143.34	$143.35	$143.30
Purchase #2	$211.38	3.571%	$218.9284	$218.93	$218.95	$218.90
Purchase #3	$232.28	10.842%	$257.4638	$257.46	$257.45	$257.50
Purchase #4	$45.32	4.615%	$47.4115	$47.41	$47.40	$47.40
Purchase #5	$114.84	11.339%	$127.8617	$127.86	$127.85	$127.90
Purchase #6	$130.47	9.538%	$142.9142	$142.91	$142.90	$142.90
Purchase #7	$83.74	4.671%	$87.6515	$87.65	$87.65	$87.70
7 purchase totals =	$945.65		$1,025.5701	$1,025.56	$1,025.55	$1,025.60