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	$55.83	9.824%	$61.3147	$61.31	$61.30	$61.30
Purchase #2	$182.29	8.716%	$198.1784	$198.18	$198.20	$198.20
Purchase #3	$109.38	13.302%	$123.9297	$123.93	$123.95	$123.90
Purchase #4	$61.33	7.321%	$65.82	$65.82	$65.80	$65.80
Purchase #5	$225.51	13.390%	$255.7058	$255.71	$255.70	$255.70
Purchase #6	$168.87	3.783%	$175.2584	$175.26	$175.25	$175.30
Purchase #7	$129.55	4.839%	$135.8189	$135.82	$135.80	$135.80
7 purchase totals =	$932.76		$1,016.0259	$1,016.03	$1,016.00	$1,016.00