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	$102.84	11.174%	$114.3313	$114.33	$114.35	$114.30
Purchase #2	$52.46	6.494%	$55.8668	$55.87	$55.85	$55.90
Purchase #3	$32.82	4.273%	$34.2224	$34.22	$34.20	$34.20
Purchase #4	$227.26	9.576%	$249.0224	$249.02	$249.00	$249.00
Purchase #5	$59.93	12.561%	$67.4578	$67.46	$67.45	$67.50
Purchase #6	$191.33	12.704%	$215.6366	$215.64	$215.65	$215.60
Purchase #7	$189.78	5.791%	$200.7702	$200.77	$200.75	$200.80
7 purchase totals =	$856.42		$937.3075	$937.31	$937.25	$937.30