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	$147.94	11.854%	$165.4768	$165.48	$165.50	$165.50
Purchase #2	$28.94	9.687%	$31.7434	$31.74	$31.75	$31.70
Purchase #3	$132.86	7.519%	$142.8497	$142.85	$142.85	$142.80
Purchase #4	$178.50	12.347%	$200.5394	$200.54	$200.55	$200.50
Purchase #5	$220.74	11.727%	$246.6262	$246.63	$246.65	$246.60
Purchase #6	$118.71	12.779%	$133.88	$133.88	$133.90	$133.90
Purchase #7	$109.69	12.517%	$123.4199	$123.42	$123.40	$123.40
7 purchase totals =	$937.38		$1,044.5354	$1,044.54	$1,044.60	$1,044.40