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	$167.51	9.226%	$182.9645	$182.96	$182.95	$183.00
Purchase #2	$23.82	13.443%	$27.0221	$27.02	$27.00	$27.00
Purchase #3	$152.86	6.601%	$162.9503	$162.95	$162.95	$163.00
Purchase #4	$250.33	4.516%	$261.6349	$261.63	$261.65	$261.60
Purchase #5	$219.69	11.635%	$245.2509	$245.25	$245.25	$245.30
Purchase #6	$243.50	6.401%	$259.0864	$259.09	$259.10	$259.10
Purchase #7	$10.79	6.801%	$11.5238	$11.52	$11.50	$11.50
7 purchase totals =	$1,068.50		$1,150.4329	$1,150.42	$1,150.40	$1,150.50