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	$248.53	6.758%	$265.3257	$265.33	$265.35	$265.30
Purchase #2	$86.52	6.846%	$92.4432	$92.44	$92.45	$92.40
Purchase #3	$159.43	13.705%	$181.2799	$181.28	$181.30	$181.30
Purchase #4	$29.26	9.668%	$32.0889	$32.09	$32.10	$32.10
Purchase #5	$177.73	10.521%	$196.429	$196.43	$196.45	$196.40
Purchase #6	$5.69	6.746%	$6.0738	$6.07	$6.05	$6.10
Purchase #7	$94.72	3.665%	$98.1915	$98.19	$98.20	$98.20
7 purchase totals =	$801.88		$871.8320	$871.83	$871.90	$871.80