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	$47.90	10.743%	$53.0459	$53.05	$53.05	$53.00
Purchase #2	$121.63	7.646%	$130.9298	$130.93	$130.95	$130.90
Purchase #3	$245.51	10.128%	$270.3753	$270.38	$270.40	$270.40
Purchase #4	$106.52	13.687%	$121.0994	$121.10	$121.10	$121.10
Purchase #5	$85.38	5.592%	$90.1544	$90.15	$90.15	$90.20
Purchase #6	$155.32	4.874%	$162.8903	$162.89	$162.90	$162.90
Purchase #7	$105.50	9.270%	$115.2799	$115.28	$115.30	$115.30
7 purchase totals =	$867.76		$943.7750	$943.78	$943.85	$943.80