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	$191.75	12.558%	$215.83	$215.83	$215.85	$215.80
Purchase #2	$58.71	7.573%	$63.1561	$63.16	$63.15	$63.20
Purchase #3	$14.69	4.491%	$15.3497	$15.35	$15.35	$15.30
Purchase #4	$160.40	4.830%	$168.1473	$168.15	$168.15	$168.10
Purchase #5	$200.86	3.822%	$208.5369	$208.54	$208.55	$208.50
Purchase #6	$194.42	6.413%	$206.8882	$206.89	$206.90	$206.90
Purchase #7	$57.32	7.230%	$61.4642	$61.46	$61.45	$61.50
7 purchase totals =	$878.15		$939.3724	$939.38	$939.40	$939.30