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	$200.71	6.838%	$214.4345	$214.43	$214.45	$214.40
Purchase #2	$200.55	5.452%	$211.484	$211.48	$211.50	$211.50
Purchase #3	$180.87	7.201%	$193.8944	$193.89	$193.90	$193.90
Purchase #4	$160.25	6.805%	$171.155	$171.16	$171.15	$171.20
Purchase #5	$84.51	6.279%	$89.8164	$89.82	$89.80	$89.80
Purchase #6	$96.29	6.507%	$102.5556	$102.56	$102.55	$102.60
Purchase #7	$81.48	5.793%	$86.2001	$86.20	$86.20	$86.20
7 purchase totals =	$1,004.66		$1,069.5400	$1,069.54	$1,069.55	$1,069.60