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	$241.76	11.639%	$269.8984	$269.90	$269.90	$269.90
Purchase #2	$52.54	12.802%	$59.2662	$59.27	$59.25	$59.30
Purchase #3	$56.28	11.457%	$62.728	$62.73	$62.75	$62.70
Purchase #4	$190.41	8.762%	$207.0937	$207.09	$207.10	$207.10
Purchase #5	$185.85	12.787%	$209.6146	$209.61	$209.60	$209.60
Purchase #6	$138.43	5.382%	$145.8803	$145.88	$145.90	$145.90
Purchase #7	$137.55	11.549%	$153.4356	$153.44	$153.45	$153.40
7 purchase totals =	$1,002.82		$1,107.9168	$1,107.92	$1,107.95	$1,107.90