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	$98.66	5.516%	$104.1021	$104.10	$104.10	$104.10
Purchase #2	$77.86	10.452%	$85.9979	$86.00	$86.00	$86.00
Purchase #3	$106.60	8.438%	$115.5949	$115.59	$115.60	$115.60
Purchase #4	$79.33	3.748%	$82.3033	$82.30	$82.30	$82.30
Purchase #5	$147.82	10.181%	$162.8696	$162.87	$162.85	$162.90
Purchase #6	$218.53	12.782%	$246.4625	$246.46	$246.45	$246.50
Purchase #7	$89.45	12.775%	$100.8772	$100.88	$100.90	$100.90
7 purchase totals =	$818.25		$898.2075	$898.20	$898.20	$898.30