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	$147.67	4.139%	$153.7821	$153.78	$153.80	$153.80
Purchase #2	$40.68	3.197%	$41.9805	$41.98	$42.00	$42.00
Purchase #3	$101.43	9.419%	$110.9837	$110.98	$111.00	$111.00
Purchase #4	$67.25	4.155%	$70.0442	$70.04	$70.05	$70.00
Purchase #5	$231.96	9.478%	$253.9452	$253.95	$253.95	$253.90
Purchase #6	$111.25	4.106%	$115.8179	$115.82	$115.80	$115.80
Purchase #7	$221.69	4.585%	$231.8545	$231.85	$231.85	$231.90
7 purchase totals =	$921.93		$978.4081	$978.40	$978.45	$978.40