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	$242.80	3.701%	$251.786	$251.79	$251.80	$251.80
Purchase #2	$100.84	4.438%	$105.3153	$105.32	$105.30	$105.30
Purchase #3	$98.34	5.688%	$103.9336	$103.93	$103.95	$103.90
Purchase #4	$43.49	6.428%	$46.2855	$46.29	$46.30	$46.30
Purchase #5	$217.38	11.738%	$242.8961	$242.90	$242.90	$242.90
Purchase #6	$29.95	6.850%	$32.0016	$32.00	$32.00	$32.00
Purchase #7	$209.54	8.401%	$227.1435	$227.14	$227.15	$227.10
7 purchase totals =	$942.34		$1,009.3616	$1,009.37	$1,009.40	$1,009.30