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	$81.47	11.776%	$91.0639	$91.06	$91.05	$91.10
Purchase #2	$201.50	12.523%	$226.7338	$226.73	$226.75	$226.70
Purchase #3	$180.41	4.126%	$187.8537	$187.85	$187.85	$187.90
Purchase #4	$219.88	9.527%	$240.828	$240.83	$240.85	$240.80
Purchase #5	$100.42	11.263%	$111.7303	$111.73	$111.75	$111.70
Purchase #6	$236.89	11.684%	$264.5682	$264.57	$264.55	$264.60
Purchase #7	$25.48	7.393%	$27.3637	$27.36	$27.35	$27.40
7 purchase totals =	$1,046.05		$1,150.1416	$1,150.13	$1,150.15	$1,150.20