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	$91.78	13.375%	$104.0556	$104.06	$104.05	$104.10
Purchase #2	$245.67	8.334%	$266.1441	$266.14	$266.15	$266.10
Purchase #3	$159.43	7.332%	$171.1194	$171.12	$171.10	$171.10
Purchase #4	$111.37	3.387%	$115.1421	$115.14	$115.15	$115.10
Purchase #5	$12.96	11.715%	$14.4783	$14.48	$14.50	$14.50
Purchase #6	$180.43	3.382%	$186.5321	$186.53	$186.55	$186.50
Purchase #7	$131.40	9.470%	$143.8436	$143.84	$143.85	$143.80
7 purchase totals =	$933.04		$1,001.3152	$1,001.31	$1,001.35	$1,001.20