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	$140.38	4.660%	$146.9217	$146.92	$146.90	$146.90
Purchase #2	$171.35	5.516%	$180.8017	$180.80	$180.80	$180.80
Purchase #3	$147.32	7.869%	$158.9126	$158.91	$158.90	$158.90
Purchase #4	$173.30	4.187%	$180.5561	$180.56	$180.55	$180.60
Purchase #5	$139.59	3.486%	$144.4561	$144.46	$144.45	$144.50
Purchase #6	$97.36	12.502%	$109.5319	$109.53	$109.55	$109.50
Purchase #7	$87.87	11.874%	$98.3037	$98.30	$98.30	$98.30
7 purchase totals =	$957.17		$1,019.4838	$1,019.48	$1,019.45	$1,019.50