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	$200.51	7.496%	$215.5402	$215.54	$215.55	$215.50
Purchase #2	$242.62	10.553%	$268.2237	$268.22	$268.20	$268.20
Purchase #3	$197.72	12.315%	$222.0692	$222.07	$222.05	$222.10
Purchase #4	$206.31	9.798%	$226.5243	$226.52	$226.50	$226.50
Purchase #5	$51.83	4.354%	$54.0867	$54.09	$54.10	$54.10
Purchase #6	$83.97	7.561%	$90.319	$90.32	$90.30	$90.30
Purchase #7	$66.58	8.765%	$72.4157	$72.42	$72.40	$72.40
7 purchase totals =	$1,049.54		$1,149.1788	$1,149.18	$1,149.10	$1,149.10