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	$49.55	10.413%	$54.7096	$54.71	$54.70	$54.70
Purchase #2	$75.59	3.301%	$78.0852	$78.09	$78.10	$78.10
Purchase #3	$14.33	11.134%	$15.9255	$15.93	$15.95	$15.90
Purchase #4	$46.71	7.264%	$50.103	$50.10	$50.10	$50.10
Purchase #5	$18.40	5.581%	$19.4269	$19.43	$19.45	$19.40
Purchase #6	$223.99	10.855%	$248.3041	$248.30	$248.30	$248.30
Purchase #7	$77.56	11.507%	$86.4848	$86.48	$86.50	$86.50
7 purchase totals =	$506.13		$553.0391	$553.04	$553.10	$553.00