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	$211.66	5.103%	$222.461	$222.46	$222.45	$222.50
Purchase #2	$213.32	10.614%	$235.9618	$235.96	$235.95	$236.00
Purchase #3	$237.42	3.410%	$245.516	$245.52	$245.50	$245.50
Purchase #4	$30.38	11.424%	$33.8506	$33.85	$33.85	$33.90
Purchase #5	$38.50	9.429%	$42.1302	$42.13	$42.15	$42.10
Purchase #6	$110.32	4.773%	$115.5856	$115.59	$115.60	$115.60
Purchase #7	$116.53	7.760%	$125.5727	$125.57	$125.55	$125.60
7 purchase totals =	$958.13		$1,021.0779	$1,021.08	$1,021.05	$1,021.20