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	$47.98	11.695%	$53.5913	$53.59	$53.60	$53.60
Purchase #2	$139.50	5.676%	$147.418	$147.42	$147.40	$147.40
Purchase #3	$139.48	8.423%	$151.2284	$151.23	$151.25	$151.20
Purchase #4	$9.34	7.592%	$10.0491	$10.05	$10.05	$10.00
Purchase #5	$68.83	4.695%	$72.0616	$72.06	$72.05	$72.10
Purchase #6	$104.41	4.549%	$109.1596	$109.16	$109.15	$109.20
Purchase #7	$158.85	11.446%	$177.032	$177.03	$177.05	$177.00
7 purchase totals =	$668.39		$720.5400	$720.54	$720.55	$720.50