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	$200.79	13.349%	$227.5935	$227.59	$227.60	$227.60
Purchase #2	$85.76	4.251%	$89.4057	$89.41	$89.40	$89.40
Purchase #3	$221.38	12.119%	$248.209	$248.21	$248.20	$248.20
Purchase #4	$211.50	9.136%	$230.8226	$230.82	$230.80	$230.80
Purchase #5	$70.68	12.177%	$79.2867	$79.29	$79.30	$79.30
Purchase #6	$61.30	7.679%	$66.0072	$66.01	$66.00	$66.00
Purchase #7	$204.55	5.222%	$215.2316	$215.23	$215.25	$215.20
7 purchase totals =	$1,055.96		$1,156.5563	$1,156.56	$1,156.55	$1,156.50