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	$246.75	7.516%	$265.2957	$265.30	$265.30	$265.30
Purchase #2	$233.62	6.355%	$248.4666	$248.47	$248.45	$248.50
Purchase #3	$57.33	7.125%	$61.4148	$61.41	$61.40	$61.40
Purchase #4	$111.88	10.199%	$123.2906	$123.29	$123.30	$123.30
Purchase #5	$132.63	4.710%	$138.8769	$138.88	$138.90	$138.90
Purchase #6	$176.64	13.346%	$200.2144	$200.21	$200.20	$200.20
Purchase #7	$110.38	12.832%	$124.544	$124.54	$124.55	$124.50
7 purchase totals =	$1,069.23		$1,162.1030	$1,162.10	$1,162.10	$1,162.10