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	$99.41	5.365%	$104.7433	$104.74	$104.75	$104.70
Purchase #2	$53.94	4.853%	$56.5577	$56.56	$56.55	$56.60
Purchase #3	$250.62	12.794%	$282.6843	$282.68	$282.70	$282.70
Purchase #4	$173.92	4.450%	$181.6594	$181.66	$181.65	$181.70
Purchase #5	$205.83	4.475%	$215.0409	$215.04	$215.05	$215.00
Purchase #6	$159.69	9.807%	$175.3508	$175.35	$175.35	$175.40
Purchase #7	$43.42	4.151%	$45.2224	$45.22	$45.20	$45.20
7 purchase totals =	$986.83		$1,061.2588	$1,061.25	$1,061.25	$1,061.30