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	$109.75	3.483%	$113.5726	$113.57	$113.55	$113.60
Purchase #2	$178.75	7.123%	$191.4824	$191.48	$191.50	$191.50
Purchase #3	$137.69	3.735%	$142.8327	$142.83	$142.85	$142.80
Purchase #4	$175.71	12.526%	$197.7194	$197.72	$197.70	$197.70
Purchase #5	$241.89	3.528%	$250.4239	$250.42	$250.40	$250.40
Purchase #6	$218.83	7.176%	$234.5332	$234.53	$234.55	$234.50
Purchase #7	$32.58	7.187%	$34.9215	$34.92	$34.90	$34.90
7 purchase totals =	$1,095.20		$1,165.4857	$1,165.47	$1,165.45	$1,165.40