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	$43.46	6.316%	$46.2049	$46.20	$46.20	$46.20
Purchase #2	$64.53	7.420%	$69.3181	$69.32	$69.30	$69.30
Purchase #3	$36.79	3.680%	$38.1439	$38.14	$38.15	$38.10
Purchase #4	$95.71	11.180%	$106.4104	$106.41	$106.40	$106.40
Purchase #5	$52.83	13.163%	$59.784	$59.78	$59.80	$59.80
Purchase #6	$138.37	4.316%	$144.342	$144.34	$144.35	$144.30
Purchase #7	$24.54	12.278%	$27.553	$27.55	$27.55	$27.60
7 purchase totals =	$456.23		$491.7563	$491.74	$491.75	$491.70