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	$160.78	4.312%	$167.7128	$167.71	$167.70	$167.70
Purchase #2	$209.57	5.128%	$220.3167	$220.32	$220.30	$220.30
Purchase #3	$30.94	4.755%	$32.4112	$32.41	$32.40	$32.40
Purchase #4	$171.47	6.112%	$181.9502	$181.95	$181.95	$182.00
Purchase #5	$109.32	8.296%	$118.3892	$118.39	$118.40	$118.40
Purchase #6	$30.99	12.634%	$34.9053	$34.91	$34.90	$34.90
Purchase #7	$213.38	4.485%	$222.9501	$222.95	$222.95	$223.00
7 purchase totals =	$926.45		$978.6355	$978.64	$978.60	$978.70