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	$65.45	7.123%	$70.112	$70.11	$70.10	$70.10
Purchase #2	$188.83	9.385%	$206.5517	$206.55	$206.55	$206.60
Purchase #3	$190.28	3.458%	$196.8599	$196.86	$196.85	$196.90
Purchase #4	$37.88	13.124%	$42.8514	$42.85	$42.85	$42.90
Purchase #5	$159.62	7.549%	$171.6697	$171.67	$171.65	$171.70
Purchase #6	$213.59	12.189%	$239.6245	$239.62	$239.60	$239.60
Purchase #7	$73.29	3.372%	$75.7613	$75.76	$75.75	$75.80
7 purchase totals =	$928.94		$1,003.4305	$1,003.42	$1,003.35	$1,003.60