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	$154.87	10.823%	$171.6316	$171.63	$171.65	$171.60
Purchase #2	$248.51	13.839%	$282.9013	$282.90	$282.90	$282.90
Purchase #3	$130.55	9.119%	$142.4549	$142.45	$142.45	$142.50
Purchase #4	$143.38	13.257%	$162.3879	$162.39	$162.40	$162.40
Purchase #5	$188.50	8.214%	$203.9834	$203.98	$204.00	$204.00
Purchase #6	$133.89	9.103%	$146.078	$146.08	$146.10	$146.10
Purchase #7	$19.88	9.428%	$21.7543	$21.75	$21.75	$21.80
7 purchase totals =	$1,019.58		$1,131.1914	$1,131.18	$1,131.25	$1,131.30