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	$115.63	13.320%	$131.0319	$131.03	$131.05	$131.00
Purchase #2	$116.31	5.725%	$122.9687	$122.97	$122.95	$123.00
Purchase #3	$18.71	9.583%	$20.503	$20.50	$20.50	$20.50
Purchase #4	$203.98	8.127%	$220.5575	$220.56	$220.55	$220.60
Purchase #5	$175.80	11.777%	$196.504	$196.50	$196.50	$196.50
Purchase #6	$163.88	6.510%	$174.5486	$174.55	$174.55	$174.50
Purchase #7	$79.92	3.546%	$82.754	$82.75	$82.75	$82.80
7 purchase totals =	$874.23		$948.8677	$948.86	$948.85	$948.90