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	$97.27	6.874%	$103.9563	$103.96	$103.95	$104.00
Purchase #2	$141.44	6.683%	$150.8924	$150.89	$150.90	$150.90
Purchase #3	$102.55	13.760%	$116.6609	$116.66	$116.65	$116.70
Purchase #4	$37.70	13.534%	$42.8023	$42.80	$42.80	$42.80
Purchase #5	$146.55	12.465%	$164.8175	$164.82	$164.80	$164.80
Purchase #6	$165.92	6.267%	$176.3182	$176.32	$176.30	$176.30
Purchase #7	$211.36	13.623%	$240.1536	$240.15	$240.15	$240.20
7 purchase totals =	$902.79		$995.6012	$995.60	$995.55	$995.70