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	$151.98	8.496%	$164.8922	$164.89	$164.90	$164.90
Purchase #2	$40.93	4.279%	$42.6814	$42.68	$42.70	$42.70
Purchase #3	$48.33	5.794%	$51.1302	$51.13	$51.15	$51.10
Purchase #4	$160.58	13.284%	$181.9114	$181.91	$181.90	$181.90
Purchase #5	$109.73	5.323%	$115.5709	$115.57	$115.55	$115.60
Purchase #6	$184.78	5.114%	$194.2296	$194.23	$194.25	$194.20
Purchase #7	$57.59	10.345%	$63.5477	$63.55	$63.55	$63.50
7 purchase totals =	$753.92		$813.9634	$813.96	$814.00	$813.90