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	$33.82	9.556%	$37.0518	$37.05	$37.05	$37.10
Purchase #2	$200.33	6.557%	$213.4656	$213.47	$213.45	$213.50
Purchase #3	$124.74	9.545%	$136.6464	$136.65	$136.65	$136.60
Purchase #4	$93.71	6.642%	$99.9342	$99.93	$99.95	$99.90
Purchase #5	$196.92	8.458%	$213.5755	$213.58	$213.60	$213.60
Purchase #6	$250.70	7.652%	$269.8836	$269.88	$269.90	$269.90
Purchase #7	$120.92	9.532%	$132.4461	$132.45	$132.45	$132.40
7 purchase totals =	$1,021.14		$1,103.0032	$1,103.01	$1,103.05	$1,103.00