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	$245.55	6.870%	$262.4193	$262.42	$262.40	$262.40
Purchase #2	$13.29	10.347%	$14.6651	$14.67	$14.65	$14.70
Purchase #3	$186.38	11.775%	$208.3262	$208.33	$208.35	$208.30
Purchase #4	$10.31	10.841%	$11.4277	$11.43	$11.45	$11.40
Purchase #5	$53.33	11.266%	$59.3382	$59.34	$59.35	$59.30
Purchase #6	$54.42	4.342%	$56.7829	$56.78	$56.80	$56.80
Purchase #7	$230.83	7.568%	$248.2992	$248.30	$248.30	$248.30
7 purchase totals =	$794.11		$861.2586	$861.27	$861.30	$861.20