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	$172.49	5.283%	$181.6026	$181.60	$181.60	$181.60
Purchase #2	$44.40	3.673%	$46.0308	$46.03	$46.05	$46.00
Purchase #3	$78.84	4.294%	$82.2254	$82.23	$82.25	$82.20
Purchase #4	$144.88	6.515%	$154.3189	$154.32	$154.30	$154.30
Purchase #5	$248.43	8.489%	$269.5192	$269.52	$269.50	$269.50
Purchase #6	$63.74	11.439%	$71.0312	$71.03	$71.05	$71.00
Purchase #7	$85.45	6.299%	$90.8325	$90.83	$90.85	$90.80
7 purchase totals =	$838.23		$895.5606	$895.56	$895.60	$895.40