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	$108.95	13.603%	$123.7705	$123.77	$123.75	$123.80
Purchase #2	$207.28	12.500%	$233.19	$233.19	$233.20	$233.20
Purchase #3	$105.47	4.162%	$109.8597	$109.86	$109.85	$109.90
Purchase #4	$65.52	9.179%	$71.5341	$71.53	$71.55	$71.50
Purchase #5	$65.92	6.788%	$70.3946	$70.39	$70.40	$70.40
Purchase #6	$204.71	7.870%	$220.8207	$220.82	$220.80	$220.80
Purchase #7	$206.68	6.144%	$219.3784	$219.38	$219.40	$219.40
7 purchase totals =	$964.53		$1,048.9480	$1,048.94	$1,048.95	$1,049.00