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	$49.38	11.537%	$55.077	$55.08	$55.10	$55.10
Purchase #2	$99.98	5.323%	$105.3019	$105.30	$105.30	$105.30
Purchase #3	$158.81	6.483%	$169.1057	$169.11	$169.10	$169.10
Purchase #4	$112.51	11.561%	$125.5173	$125.52	$125.50	$125.50
Purchase #5	$39.88	6.445%	$42.4503	$42.45	$42.45	$42.50
Purchase #6	$71.94	10.441%	$79.4513	$79.45	$79.45	$79.50
Purchase #7	$118.50	4.102%	$123.3609	$123.36	$123.35	$123.40
7 purchase totals =	$651.00		$700.2644	$700.27	$700.25	$700.40