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	$187.91	5.483%	$198.2131	$198.21	$198.20	$198.20
Purchase #2	$243.42	7.754%	$262.2948	$262.29	$262.30	$262.30
Purchase #3	$160.30	5.782%	$169.5685	$169.57	$169.55	$169.60
Purchase #4	$92.96	5.802%	$98.3535	$98.35	$98.35	$98.40
Purchase #5	$106.78	4.519%	$111.6054	$111.61	$111.60	$111.60
Purchase #6	$163.45	3.267%	$168.7899	$168.79	$168.80	$168.80
Purchase #7	$7.60	12.480%	$8.5485	$8.55	$8.55	$8.50
7 purchase totals =	$962.42		$1,017.3737	$1,017.37	$1,017.35	$1,017.40