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	$209.69	8.677%	$227.8848	$227.88	$227.90	$227.90
Purchase #2	$236.88	9.371%	$259.078	$259.08	$259.10	$259.10
Purchase #3	$62.36	8.113%	$67.4193	$67.42	$67.40	$67.40
Purchase #4	$131.65	7.787%	$141.9016	$141.90	$141.90	$141.90
Purchase #5	$149.92	4.188%	$156.1986	$156.20	$156.20	$156.20
Purchase #6	$137.71	7.104%	$147.4929	$147.49	$147.50	$147.50
Purchase #7	$106.59	5.504%	$112.4567	$112.46	$112.45	$112.50
7 purchase totals =	$1,034.80		$1,112.4319	$1,112.43	$1,112.45	$1,112.50