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	$169.63	12.746%	$191.251	$191.25	$191.25	$191.30
Purchase #2	$128.46	6.817%	$137.2171	$137.22	$137.20	$137.20
Purchase #3	$153.80	8.777%	$167.299	$167.30	$167.30	$167.30
Purchase #4	$72.25	7.272%	$77.504	$77.50	$77.50	$77.50
Purchase #5	$39.65	7.119%	$42.4727	$42.47	$42.45	$42.50
Purchase #6	$62.97	6.215%	$66.8836	$66.88	$66.90	$66.90
Purchase #7	$77.66	5.116%	$81.6331	$81.63	$81.65	$81.60
7 purchase totals =	$704.42		$764.2605	$764.25	$764.25	$764.30