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	$205.89	13.522%	$233.7304	$233.73	$233.75	$233.70
Purchase #2	$228.85	11.280%	$254.6643	$254.66	$254.65	$254.70
Purchase #3	$24.77	12.681%	$27.9111	$27.91	$27.90	$27.90
Purchase #4	$127.44	11.137%	$141.633	$141.63	$141.65	$141.60
Purchase #5	$179.53	11.865%	$200.8312	$200.83	$200.85	$200.80
Purchase #6	$188.41	4.826%	$197.5027	$197.50	$197.50	$197.50
Purchase #7	$84.48	8.680%	$91.8129	$91.81	$91.80	$91.80
7 purchase totals =	$1,039.37		$1,148.0856	$1,148.07	$1,148.10	$1,148.00