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	$86.55	4.695%	$90.6135	$90.61	$90.60	$90.60
Purchase #2	$213.36	4.784%	$223.5671	$223.57	$223.55	$223.60
Purchase #3	$159.65	7.469%	$171.5743	$171.57	$171.55	$171.60
Purchase #4	$164.78	10.822%	$182.6125	$182.61	$182.60	$182.60
Purchase #5	$169.26	11.631%	$188.9466	$188.95	$188.95	$188.90
Purchase #6	$138.67	11.802%	$155.0358	$155.04	$155.05	$155.00
Purchase #7	$143.41	8.821%	$156.0602	$156.06	$156.05	$156.10
7 purchase totals =	$1,075.68		$1,168.4100	$1,168.41	$1,168.35	$1,168.40