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	$185.44	10.843%	$205.5473	$205.55	$205.55	$205.50
Purchase #2	$77.39	10.130%	$85.2296	$85.23	$85.25	$85.20
Purchase #3	$43.93	12.209%	$49.2934	$49.29	$49.30	$49.30
Purchase #4	$124.36	3.134%	$128.2574	$128.26	$128.25	$128.30
Purchase #5	$130.63	12.197%	$146.5629	$146.56	$146.55	$146.60
Purchase #6	$92.33	12.221%	$103.6136	$103.61	$103.60	$103.60
Purchase #7	$73.27	12.628%	$82.5225	$82.52	$82.50	$82.50
7 purchase totals =	$727.35		$801.0267	$801.02	$801.00	$801.00