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	$118.82	7.825%	$128.1177	$128.12	$128.10	$128.10
Purchase #2	$121.81	10.308%	$134.3662	$134.37	$134.35	$134.40
Purchase #3	$144.78	13.715%	$164.6366	$164.64	$164.65	$164.60
Purchase #4	$91.62	9.670%	$100.4797	$100.48	$100.50	$100.50
Purchase #5	$245.93	8.627%	$267.1464	$267.15	$267.15	$267.10
Purchase #6	$112.89	12.538%	$127.0441	$127.04	$127.05	$127.00
Purchase #7	$184.33	4.375%	$192.3944	$192.39	$192.40	$192.40
7 purchase totals =	$1,020.18		$1,114.1851	$1,114.19	$1,114.20	$1,114.10