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	$86.78	10.309%	$95.7262	$95.73	$95.75	$95.70
Purchase #2	$44.72	13.787%	$50.8855	$50.89	$50.90	$50.90
Purchase #3	$55.52	7.315%	$59.5813	$59.58	$59.60	$59.60
Purchase #4	$211.64	7.338%	$227.1701	$227.17	$227.15	$227.20
Purchase #5	$136.73	4.311%	$142.6244	$142.62	$142.60	$142.60
Purchase #6	$96.43	13.604%	$109.5483	$109.55	$109.55	$109.50
Purchase #7	$100.26	4.720%	$104.9923	$104.99	$105.00	$105.00
7 purchase totals =	$732.08		$790.5281	$790.53	$790.55	$790.50