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	$53.91	5.616%	$56.9376	$56.94	$56.95	$56.90
Purchase #2	$90.48	3.297%	$93.4631	$93.46	$93.45	$93.50
Purchase #3	$33.98	6.773%	$36.2815	$36.28	$36.30	$36.30
Purchase #4	$146.84	10.701%	$162.5533	$162.55	$162.55	$162.60
Purchase #5	$83.42	13.440%	$94.6316	$94.63	$94.65	$94.60
Purchase #6	$14.63	8.623%	$15.8915	$15.89	$15.90	$15.90
Purchase #7	$133.27	6.505%	$141.9392	$141.94	$141.95	$141.90
7 purchase totals =	$556.53		$601.6978	$601.69	$601.75	$601.70