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	$51.78	5.173%	$54.4586	$54.46	$54.45	$54.50
Purchase #2	$66.42	4.740%	$69.5683	$69.57	$69.55	$69.60
Purchase #3	$135.96	5.584%	$143.552	$143.55	$143.55	$143.60
Purchase #4	$104.93	3.712%	$108.825	$108.83	$108.85	$108.80
Purchase #5	$235.25	5.541%	$248.2852	$248.29	$248.30	$248.30
Purchase #6	$213.65	4.654%	$223.5933	$223.59	$223.60	$223.60
Purchase #7	$70.74	3.316%	$73.0857	$73.09	$73.10	$73.10
7 purchase totals =	$878.73		$921.3681	$921.38	$921.40	$921.50