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	$68.25	7.487%	$73.3599	$73.36	$73.35	$73.40
Purchase #2	$213.54	6.287%	$226.9653	$226.97	$226.95	$227.00
Purchase #3	$78.96	4.459%	$82.4808	$82.48	$82.50	$82.50
Purchase #4	$116.78	5.763%	$123.51	$123.51	$123.50	$123.50
Purchase #5	$18.85	9.647%	$20.6685	$20.67	$20.65	$20.70
Purchase #6	$54.86	11.708%	$61.283	$61.28	$61.30	$61.30
Purchase #7	$207.67	3.560%	$215.0631	$215.06	$215.05	$215.10
7 purchase totals =	$758.91		$803.3306	$803.33	$803.30	$803.50