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	$64.72	12.683%	$72.9284	$72.93	$72.95	$72.90
Purchase #2	$54.76	4.365%	$57.1503	$57.15	$57.15	$57.20
Purchase #3	$32.85	11.270%	$36.5522	$36.55	$36.55	$36.60
Purchase #4	$213.87	13.567%	$242.8857	$242.89	$242.90	$242.90
Purchase #5	$204.86	6.851%	$218.895	$218.90	$218.90	$218.90
Purchase #6	$219.73	11.680%	$245.3945	$245.39	$245.40	$245.40
Purchase #7	$7.60	4.166%	$7.9166	$7.92	$7.90	$7.90
7 purchase totals =	$798.39		$881.7227	$881.73	$881.75	$881.80