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	$50.88	4.847%	$53.3462	$53.35	$53.35	$53.30
Purchase #2	$54.33	9.586%	$59.5381	$59.54	$59.55	$59.50
Purchase #3	$119.56	10.392%	$131.9847	$131.98	$132.00	$132.00
Purchase #4	$185.28	5.461%	$195.3981	$195.40	$195.40	$195.40
Purchase #5	$85.38	5.338%	$89.9376	$89.94	$89.95	$89.90
Purchase #6	$56.73	8.373%	$61.48	$61.48	$61.50	$61.50
Purchase #7	$115.48	6.704%	$123.2218	$123.22	$123.20	$123.20
7 purchase totals =	$667.64		$714.9065	$714.91	$714.95	$714.80