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	$96.94	11.668%	$108.251	$108.25	$108.25	$108.30
Purchase #2	$122.54	4.235%	$127.7296	$127.73	$127.75	$127.70
Purchase #3	$51.32	12.143%	$57.5518	$57.55	$57.55	$57.60
Purchase #4	$146.56	7.828%	$158.0327	$158.03	$158.05	$158.00
Purchase #5	$195.51	13.365%	$221.6399	$221.64	$221.65	$221.60
Purchase #6	$211.34	3.833%	$219.4407	$219.44	$219.45	$219.40
Purchase #7	$172.92	12.302%	$194.1926	$194.19	$194.20	$194.20
7 purchase totals =	$997.13		$1,086.8383	$1,086.83	$1,086.90	$1,086.80