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	$133.70	10.857%	$148.2158	$148.22	$148.20	$148.20
Purchase #2	$94.88	6.252%	$100.8119	$100.81	$100.80	$100.80
Purchase #3	$19.86	3.473%	$20.5497	$20.55	$20.55	$20.50
Purchase #4	$139.95	5.803%	$148.0713	$148.07	$148.05	$148.10
Purchase #5	$119.63	6.486%	$127.3892	$127.39	$127.40	$127.40
Purchase #6	$103.56	6.755%	$110.5555	$110.56	$110.55	$110.60
Purchase #7	$221.58	5.531%	$233.8356	$233.84	$233.85	$233.80
7 purchase totals =	$833.16		$889.4290	$889.44	$889.40	$889.40