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	$115.85	6.575%	$123.4671	$123.47	$123.45	$123.50
Purchase #2	$202.67	5.818%	$214.4613	$214.46	$214.45	$214.50
Purchase #3	$173.35	5.466%	$182.8253	$182.83	$182.85	$182.80
Purchase #4	$233.93	7.216%	$250.8104	$250.81	$250.80	$250.80
Purchase #5	$29.48	10.486%	$32.5713	$32.57	$32.55	$32.60
Purchase #6	$223.30	12.640%	$251.5251	$251.53	$251.55	$251.50
Purchase #7	$53.79	7.154%	$57.6381	$57.64	$57.65	$57.60
7 purchase totals =	$1,032.37		$1,113.2986	$1,113.31	$1,113.30	$1,113.30