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	$181.52	7.677%	$195.4553	$195.46	$195.45	$195.50
Purchase #2	$69.67	12.484%	$78.3676	$78.37	$78.35	$78.40
Purchase #3	$103.96	11.504%	$115.9196	$115.92	$115.90	$115.90
Purchase #4	$102.58	7.763%	$110.5433	$110.54	$110.55	$110.50
Purchase #5	$95.61	5.722%	$101.0808	$101.08	$101.10	$101.10
Purchase #6	$71.54	10.151%	$78.802	$78.80	$78.80	$78.80
Purchase #7	$249.52	10.758%	$276.3634	$276.36	$276.35	$276.40
7 purchase totals =	$874.40		$956.5320	$956.53	$956.50	$956.60