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	$168.30	9.813%	$184.8153	$184.82	$184.80	$184.80
Purchase #2	$209.49	4.278%	$218.452	$218.45	$218.45	$218.50
Purchase #3	$103.41	3.751%	$107.2889	$107.29	$107.30	$107.30
Purchase #4	$194.28	9.796%	$213.3117	$213.31	$213.30	$213.30
Purchase #5	$109.48	4.368%	$114.2621	$114.26	$114.25	$114.30
Purchase #6	$135.59	5.429%	$142.9512	$142.95	$142.95	$143.00
Purchase #7	$53.86	10.294%	$59.4043	$59.40	$59.40	$59.40
7 purchase totals =	$974.41		$1,040.4855	$1,040.48	$1,040.45	$1,040.60