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	$150.85	10.760%	$167.0815	$167.08	$167.10	$167.10
Purchase #2	$18.89	6.550%	$20.1273	$20.13	$20.15	$20.10
Purchase #3	$124.27	5.641%	$131.2801	$131.28	$131.30	$131.30
Purchase #4	$148.78	13.688%	$169.145	$169.15	$169.15	$169.10
Purchase #5	$91.59	3.218%	$94.5374	$94.54	$94.55	$94.50
Purchase #6	$233.87	4.591%	$244.607	$244.61	$244.60	$244.60
Purchase #7	$78.80	10.314%	$86.9274	$86.93	$86.95	$86.90
7 purchase totals =	$847.05		$913.7057	$913.72	$913.80	$913.60