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	$93.70	8.758%	$101.9062	$101.91	$101.90	$101.90
Purchase #2	$82.92	7.765%	$89.3587	$89.36	$89.35	$89.40
Purchase #3	$81.50	11.218%	$90.6427	$90.64	$90.65	$90.60
Purchase #4	$30.59	8.630%	$33.2299	$33.23	$33.25	$33.20
Purchase #5	$152.49	8.555%	$165.5355	$165.54	$165.55	$165.50
Purchase #6	$183.25	8.103%	$198.0987	$198.10	$198.10	$198.10
Purchase #7	$184.32	10.471%	$203.6201	$203.62	$203.60	$203.60
7 purchase totals =	$808.77		$882.3918	$882.40	$882.40	$882.30