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	$57.77	13.692%	$65.6799	$65.68	$65.70	$65.70
Purchase #2	$143.65	4.750%	$150.4734	$150.47	$150.45	$150.50
Purchase #3	$162.73	5.609%	$171.8575	$171.86	$171.85	$171.90
Purchase #4	$61.32	10.407%	$67.7016	$67.70	$67.70	$67.70
Purchase #5	$27.87	12.475%	$31.3468	$31.35	$31.35	$31.30
Purchase #6	$222.46	10.404%	$245.6047	$245.60	$245.60	$245.60
Purchase #7	$159.69	12.165%	$179.1163	$179.12	$179.10	$179.10
7 purchase totals =	$835.49		$911.7802	$911.78	$911.75	$911.80