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	$114.77	11.349%	$127.7952	$127.80	$127.80	$127.80
Purchase #2	$187.66	13.663%	$213.3	$213.30	$213.30	$213.30
Purchase #3	$169.58	6.315%	$180.289	$180.29	$180.30	$180.30
Purchase #4	$147.50	11.666%	$164.7074	$164.71	$164.70	$164.70
Purchase #5	$228.33	11.859%	$255.4077	$255.41	$255.40	$255.40
Purchase #6	$76.92	5.105%	$80.8468	$80.85	$80.85	$80.80
Purchase #7	$96.29	4.438%	$100.5634	$100.56	$100.55	$100.60
7 purchase totals =	$1,021.05		$1,122.9095	$1,122.92	$1,122.90	$1,122.90