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	$120.79	13.786%	$137.4421	$137.44	$137.45	$137.40
Purchase #2	$5.54	10.474%	$6.1203	$6.12	$6.10	$6.10
Purchase #3	$67.97	6.822%	$72.6069	$72.61	$72.60	$72.60
Purchase #4	$72.73	13.647%	$82.6555	$82.66	$82.65	$82.70
Purchase #5	$127.54	7.329%	$136.8874	$136.89	$136.90	$136.90
Purchase #6	$49.67	4.274%	$51.7929	$51.79	$51.80	$51.80
Purchase #7	$200.30	4.818%	$209.9505	$209.95	$209.95	$210.00
7 purchase totals =	$644.54		$697.4556	$697.46	$697.45	$697.50