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	$72.96	10.722%	$80.7828	$80.78	$80.80	$80.80
Purchase #2	$165.27	6.560%	$176.1117	$176.11	$176.10	$176.10
Purchase #3	$176.63	7.755%	$190.3277	$190.33	$190.35	$190.30
Purchase #4	$232.65	10.278%	$256.5618	$256.56	$256.55	$256.60
Purchase #5	$165.37	5.340%	$174.2008	$174.20	$174.20	$174.20
Purchase #6	$27.40	5.188%	$28.8215	$28.82	$28.80	$28.80
Purchase #7	$146.49	5.282%	$154.2276	$154.23	$154.25	$154.20
7 purchase totals =	$986.77		$1,061.0339	$1,061.03	$1,061.05	$1,061.00