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	$93.86	6.333%	$99.8042	$99.80	$99.80	$99.80
Purchase #2	$63.86	5.769%	$67.5441	$67.54	$67.55	$67.50
Purchase #3	$145.36	3.440%	$150.3604	$150.36	$150.35	$150.40
Purchase #4	$242.90	4.568%	$253.9957	$254.00	$254.00	$254.00
Purchase #5	$112.30	10.290%	$123.8557	$123.86	$123.85	$123.90
Purchase #6	$197.39	11.309%	$219.7128	$219.71	$219.70	$219.70
Purchase #7	$43.63	7.258%	$46.7967	$46.80	$46.80	$46.80
7 purchase totals =	$899.30		$962.0696	$962.07	$962.05	$962.10