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	$158.87	9.870%	$174.5505	$174.55	$174.55	$174.60
Purchase #2	$41.30	5.272%	$43.4773	$43.48	$43.50	$43.50
Purchase #3	$173.31	10.489%	$191.4885	$191.49	$191.50	$191.50
Purchase #4	$63.85	9.305%	$69.7912	$69.79	$69.80	$69.80
Purchase #5	$188.90	13.250%	$213.9293	$213.93	$213.95	$213.90
Purchase #6	$219.87	3.381%	$227.3038	$227.30	$227.30	$227.30
Purchase #7	$65.51	11.203%	$72.8491	$72.85	$72.85	$72.80
7 purchase totals =	$911.61		$993.3897	$993.39	$993.45	$993.40