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	$248.50	4.352%	$259.3147	$259.31	$259.30	$259.30
Purchase #2	$19.98	7.849%	$21.5482	$21.55	$21.55	$21.50
Purchase #3	$171.54	5.819%	$181.5219	$181.52	$181.50	$181.50
Purchase #4	$48.41	11.405%	$53.9312	$53.93	$53.95	$53.90
Purchase #5	$161.81	4.154%	$168.5316	$168.53	$168.55	$168.50
Purchase #6	$139.59	4.827%	$146.328	$146.33	$146.35	$146.30
Purchase #7	$16.70	7.576%	$17.9652	$17.97	$17.95	$18.00
7 purchase totals =	$806.53		$849.1408	$849.14	$849.15	$849.00