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	$118.38	11.460%	$131.9463	$131.95	$131.95	$131.90
Purchase #2	$181.82	3.650%	$188.4564	$188.46	$188.45	$188.50
Purchase #3	$168.71	13.366%	$191.2598	$191.26	$191.25	$191.30
Purchase #4	$100.49	5.208%	$105.7235	$105.72	$105.70	$105.70
Purchase #5	$63.62	5.436%	$67.0784	$67.08	$67.10	$67.10
Purchase #6	$114.84	13.498%	$130.3411	$130.34	$130.35	$130.30
Purchase #7	$80.82	13.555%	$91.7752	$91.78	$91.80	$91.80
7 purchase totals =	$828.68		$906.5807	$906.59	$906.60	$906.60