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	$78.92	5.113%	$82.9552	$82.96	$82.95	$83.00
Purchase #2	$123.27	3.408%	$127.471	$127.47	$127.45	$127.50
Purchase #3	$224.39	12.780%	$253.067	$253.07	$253.05	$253.10
Purchase #4	$173.67	13.587%	$197.2665	$197.27	$197.25	$197.30
Purchase #5	$238.87	9.817%	$262.3199	$262.32	$262.30	$262.30
Purchase #6	$48.97	10.706%	$54.2127	$54.21	$54.20	$54.20
Purchase #7	$78.88	13.780%	$89.7497	$89.75	$89.75	$89.70
7 purchase totals =	$966.97		$1,067.0420	$1,067.05	$1,066.95	$1,067.10