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	$101.56	4.113%	$105.7372	$105.74	$105.75	$105.70
Purchase #2	$185.91	5.727%	$196.5571	$196.56	$196.55	$196.60
Purchase #3	$224.32	5.451%	$236.5477	$236.55	$236.55	$236.50
Purchase #4	$171.40	7.712%	$184.6184	$184.62	$184.60	$184.60
Purchase #5	$195.96	11.521%	$218.5366	$218.54	$218.55	$218.50
Purchase #6	$171.80	10.809%	$190.3699	$190.37	$190.35	$190.40
Purchase #7	$237.69	12.425%	$267.223	$267.22	$267.20	$267.20
7 purchase totals =	$1,288.64		$1,399.5899	$1,399.60	$1,399.55	$1,399.50