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	$162.39	12.485%	$182.6644	$182.66	$182.65	$182.70
Purchase #2	$105.88	3.820%	$109.9246	$109.92	$109.90	$109.90
Purchase #3	$32.28	3.403%	$33.3785	$33.38	$33.40	$33.40
Purchase #4	$246.95	3.786%	$256.2995	$256.30	$256.30	$256.30
Purchase #5	$129.54	12.402%	$145.6056	$145.61	$145.60	$145.60
Purchase #6	$240.32	11.648%	$268.3125	$268.31	$268.30	$268.30
Purchase #7	$88.61	9.600%	$97.1166	$97.12	$97.10	$97.10
7 purchase totals =	$1,005.97		$1,093.3017	$1,093.30	$1,093.25	$1,093.30