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	$49.67	9.254%	$54.2665	$54.27	$54.25	$54.30
Purchase #2	$74.88	10.219%	$82.532	$82.53	$82.55	$82.50
Purchase #3	$178.71	7.573%	$192.2437	$192.24	$192.25	$192.20
Purchase #4	$39.30	3.272%	$40.5859	$40.59	$40.60	$40.60
Purchase #5	$164.33	3.165%	$169.531	$169.53	$169.55	$169.50
Purchase #6	$21.59	10.453%	$23.8468	$23.85	$23.85	$23.80
Purchase #7	$80.83	11.830%	$90.3922	$90.39	$90.40	$90.40
7 purchase totals =	$609.31		$653.3981	$653.40	$653.45	$653.30