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	$159.90	8.447%	$173.4068	$173.41	$173.40	$173.40
Purchase #2	$82.42	5.648%	$87.0751	$87.08	$87.10	$87.10
Purchase #3	$167.34	9.578%	$183.3678	$183.37	$183.35	$183.40
Purchase #4	$74.63	10.593%	$82.5356	$82.54	$82.55	$82.50
Purchase #5	$159.31	13.174%	$180.2975	$180.30	$180.30	$180.30
Purchase #6	$160.94	5.271%	$169.4231	$169.42	$169.40	$169.40
Purchase #7	$196.56	13.308%	$222.7182	$222.72	$222.70	$222.70
7 purchase totals =	$1,001.10		$1,098.8241	$1,098.84	$1,098.80	$1,098.80