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	$110.31	8.354%	$119.5253	$119.53	$119.55	$119.50
Purchase #2	$54.94	5.477%	$57.9491	$57.95	$57.95	$57.90
Purchase #3	$72.31	11.447%	$80.5873	$80.59	$80.60	$80.60
Purchase #4	$162.94	10.361%	$179.8222	$179.82	$179.80	$179.80
Purchase #5	$152.50	13.412%	$172.9533	$172.95	$172.95	$173.00
Purchase #6	$86.73	13.133%	$98.1203	$98.12	$98.10	$98.10
Purchase #7	$179.50	11.588%	$200.3005	$200.30	$200.30	$200.30
7 purchase totals =	$819.23		$909.2580	$909.26	$909.25	$909.20