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	$230.42	5.153%	$242.2935	$242.29	$242.30	$242.30
Purchase #2	$68.70	13.547%	$78.0068	$78.01	$78.00	$78.00
Purchase #3	$188.56	6.308%	$200.4544	$200.45	$200.45	$200.50
Purchase #4	$249.93	10.238%	$275.5178	$275.52	$275.50	$275.50
Purchase #5	$174.52	12.522%	$196.3734	$196.37	$196.35	$196.40
Purchase #6	$152.58	7.765%	$164.4278	$164.43	$164.45	$164.40
Purchase #7	$196.76	8.161%	$212.8176	$212.82	$212.80	$212.80
7 purchase totals =	$1,261.47		$1,369.8913	$1,369.89	$1,369.85	$1,369.90