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	$96.49	9.368%	$105.5292	$105.53	$105.55	$105.50
Purchase #2	$37.52	4.352%	$39.1529	$39.15	$39.15	$39.20
Purchase #3	$178.58	7.266%	$191.5556	$191.56	$191.55	$191.60
Purchase #4	$43.63	6.447%	$46.4428	$46.44	$46.45	$46.40
Purchase #5	$39.26	11.520%	$43.7828	$43.78	$43.80	$43.80
Purchase #6	$134.34	5.321%	$141.4882	$141.49	$141.50	$141.50
Purchase #7	$146.78	10.627%	$162.3783	$162.38	$162.40	$162.40
7 purchase totals =	$676.60		$730.3298	$730.33	$730.40	$730.40