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	$213.98	6.419%	$227.7154	$227.72	$227.70	$227.70
Purchase #2	$83.82	10.494%	$92.6161	$92.62	$92.60	$92.60
Purchase #3	$22.61	9.693%	$24.8016	$24.80	$24.80	$24.80
Purchase #4	$165.50	9.527%	$181.2672	$181.27	$181.25	$181.30
Purchase #5	$35.56	5.190%	$37.4056	$37.41	$37.40	$37.40
Purchase #6	$179.81	13.197%	$203.5395	$203.54	$203.55	$203.50
Purchase #7	$46.94	12.436%	$52.7775	$52.78	$52.80	$52.80
7 purchase totals =	$748.22		$820.1229	$820.14	$820.10	$820.10