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	$118.83	7.635%	$127.9027	$127.90	$127.90	$127.90
Purchase #2	$148.39	11.136%	$164.9147	$164.91	$164.90	$164.90
Purchase #3	$111.85	7.591%	$120.3405	$120.34	$120.35	$120.30
Purchase #4	$156.47	11.636%	$174.6768	$174.68	$174.70	$174.70
Purchase #5	$241.40	3.525%	$249.9094	$249.91	$249.90	$249.90
Purchase #6	$37.59	8.544%	$40.8017	$40.80	$40.80	$40.80
Purchase #7	$203.38	12.263%	$228.3205	$228.32	$228.30	$228.30
7 purchase totals =	$1,017.91		$1,106.8663	$1,106.86	$1,106.85	$1,106.80