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	$35.84	4.791%	$37.5571	$37.56	$37.55	$37.60
Purchase #2	$38.28	9.787%	$42.0265	$42.03	$42.05	$42.00
Purchase #3	$69.30	13.795%	$78.8599	$78.86	$78.85	$78.90
Purchase #4	$32.26	9.775%	$35.4134	$35.41	$35.40	$35.40
Purchase #5	$201.60	7.412%	$216.5426	$216.54	$216.55	$216.50
Purchase #6	$221.40	13.763%	$251.8713	$251.87	$251.85	$251.90
Purchase #7	$176.70	4.150%	$184.0331	$184.03	$184.05	$184.00
7 purchase totals =	$775.38		$846.3039	$846.30	$846.30	$846.30