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	$55.33	10.414%	$61.0921	$61.09	$61.10	$61.10
Purchase #2	$200.54	9.558%	$219.7076	$219.71	$219.70	$219.70
Purchase #3	$30.96	13.398%	$35.108	$35.11	$35.10	$35.10
Purchase #4	$222.64	11.639%	$248.5531	$248.55	$248.55	$248.60
Purchase #5	$33.94	10.746%	$37.5872	$37.59	$37.60	$37.60
Purchase #6	$87.46	5.845%	$92.572	$92.57	$92.55	$92.60
Purchase #7	$196.82	9.493%	$215.5041	$215.50	$215.50	$215.50
7 purchase totals =	$827.69		$910.1241	$910.12	$910.10	$910.20