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	$126.93	3.718%	$131.6493	$131.65	$131.65	$131.60
Purchase #2	$167.93	10.833%	$186.1219	$186.12	$186.10	$186.10
Purchase #3	$112.41	5.715%	$118.8342	$118.83	$118.85	$118.80
Purchase #4	$61.31	13.418%	$69.5366	$69.54	$69.55	$69.50
Purchase #5	$175.41	8.767%	$190.7882	$190.79	$190.80	$190.80
Purchase #6	$233.64	7.273%	$250.6326	$250.63	$250.65	$250.60
Purchase #7	$209.47	3.479%	$216.7575	$216.76	$216.75	$216.80
7 purchase totals =	$1,087.10		$1,164.3203	$1,164.32	$1,164.35	$1,164.20