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	$86.27	3.427%	$89.2265	$89.23	$89.25	$89.20
Purchase #2	$120.88	10.636%	$133.7368	$133.74	$133.75	$133.70
Purchase #3	$37.41	3.295%	$38.6427	$38.64	$38.65	$38.60
Purchase #4	$98.71	10.460%	$109.0351	$109.04	$109.05	$109.00
Purchase #5	$190.91	9.329%	$208.72	$208.72	$208.70	$208.70
Purchase #6	$243.55	13.435%	$276.2709	$276.27	$276.25	$276.30
Purchase #7	$226.33	9.839%	$248.5986	$248.60	$248.60	$248.60
7 purchase totals =	$1,004.06		$1,104.2306	$1,104.24	$1,104.25	$1,104.10