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	$49.54	9.283%	$54.1388	$54.14	$54.15	$54.10
Purchase #2	$204.96	4.213%	$213.595	$213.60	$213.60	$213.60
Purchase #3	$150.71	12.121%	$168.9776	$168.98	$169.00	$169.00
Purchase #4	$59.48	4.645%	$62.2428	$62.24	$62.25	$62.20
Purchase #5	$225.53	12.867%	$254.5489	$254.55	$254.55	$254.50
Purchase #6	$94.86	9.138%	$103.5283	$103.53	$103.55	$103.50
Purchase #7	$217.28	5.633%	$229.5194	$229.52	$229.50	$229.50
7 purchase totals =	$1,002.36		$1,086.5508	$1,086.56	$1,086.60	$1,086.40