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	$130.97	10.430%	$144.6302	$144.63	$144.65	$144.60
Purchase #2	$84.28	12.230%	$94.5874	$94.59	$94.60	$94.60
Purchase #3	$219.76	6.264%	$233.5258	$233.53	$233.55	$233.50
Purchase #4	$44.52	10.727%	$49.2957	$49.30	$49.30	$49.30
Purchase #5	$57.73	4.674%	$60.4283	$60.43	$60.45	$60.40
Purchase #6	$222.71	10.121%	$245.2505	$245.25	$245.25	$245.30
Purchase #7	$200.42	7.545%	$215.5417	$215.54	$215.55	$215.50
7 purchase totals =	$960.39		$1,043.2596	$1,043.27	$1,043.35	$1,043.20