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	$131.51	9.529%	$144.0416	$144.04	$144.05	$144.00
Purchase #2	$156.28	5.510%	$164.891	$164.89	$164.90	$164.90
Purchase #3	$179.39	8.369%	$194.4031	$194.40	$194.40	$194.40
Purchase #4	$30.60	3.251%	$31.5948	$31.59	$31.60	$31.60
Purchase #5	$229.32	13.360%	$259.9572	$259.96	$259.95	$260.00
Purchase #6	$203.38	13.229%	$230.2851	$230.29	$230.30	$230.30
Purchase #7	$29.55	5.323%	$31.1229	$31.12	$31.10	$31.10
7 purchase totals =	$960.03		$1,056.2957	$1,056.29	$1,056.30	$1,056.30