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	$92.70	7.370%	$99.532	$99.53	$99.55	$99.50
Purchase #2	$58.47	5.287%	$61.5613	$61.56	$61.55	$61.60
Purchase #3	$181.60	13.338%	$205.8218	$205.82	$205.80	$205.80
Purchase #4	$153.98	12.252%	$172.8456	$172.85	$172.85	$172.80
Purchase #5	$240.53	13.748%	$273.5981	$273.60	$273.60	$273.60
Purchase #6	$36.34	11.795%	$40.6263	$40.63	$40.65	$40.60
Purchase #7	$64.26	6.666%	$68.5436	$68.54	$68.55	$68.50
7 purchase totals =	$827.88		$922.5287	$922.53	$922.55	$922.40