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	$164.71	4.117%	$171.4911	$171.49	$171.50	$171.50
Purchase #2	$87.56	3.227%	$90.3856	$90.39	$90.40	$90.40
Purchase #3	$90.69	7.309%	$97.3185	$97.32	$97.30	$97.30
Purchase #4	$117.96	5.310%	$124.2237	$124.22	$124.20	$124.20
Purchase #5	$191.51	3.589%	$198.3833	$198.38	$198.40	$198.40
Purchase #6	$115.45	11.297%	$128.4924	$128.49	$128.50	$128.50
Purchase #7	$189.61	8.743%	$206.1876	$206.19	$206.20	$206.20
7 purchase totals =	$957.49		$1,016.4822	$1,016.48	$1,016.50	$1,016.50