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	$164.32	12.607%	$185.0358	$185.04	$185.05	$185.00
Purchase #2	$63.82	7.421%	$68.5561	$68.56	$68.55	$68.60
Purchase #3	$144.83	7.229%	$155.2998	$155.30	$155.30	$155.30
Purchase #4	$193.55	13.602%	$219.8767	$219.88	$219.90	$219.90
Purchase #5	$190.78	5.149%	$200.6033	$200.60	$200.60	$200.60
Purchase #6	$199.70	7.735%	$215.1468	$215.15	$215.15	$215.10
Purchase #7	$99.79	7.172%	$106.9469	$106.95	$106.95	$106.90
7 purchase totals =	$1,056.79		$1,151.4654	$1,151.48	$1,151.50	$1,151.40