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	$149.60	3.550%	$154.9108	$154.91	$154.90	$154.90
Purchase #2	$167.91	5.716%	$177.5077	$177.51	$177.50	$177.50
Purchase #3	$225.72	3.512%	$233.6473	$233.65	$233.65	$233.60
Purchase #4	$90.31	12.815%	$101.8832	$101.88	$101.90	$101.90
Purchase #5	$125.74	12.660%	$141.6587	$141.66	$141.65	$141.70
Purchase #6	$26.62	4.783%	$27.8932	$27.89	$27.90	$27.90
Purchase #7	$165.47	8.459%	$179.4671	$179.47	$179.45	$179.50
7 purchase totals =	$951.37		$1,016.9680	$1,016.97	$1,016.95	$1,017.00