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	$187.84	13.116%	$212.4771	$212.48	$212.50	$212.50
Purchase #2	$86.45	5.435%	$91.1486	$91.15	$91.15	$91.10
Purchase #3	$118.77	4.400%	$123.9959	$124.00	$124.00	$124.00
Purchase #4	$48.45	11.614%	$54.077	$54.08	$54.10	$54.10
Purchase #5	$216.85	10.873%	$240.4281	$240.43	$240.45	$240.40
Purchase #6	$189.77	12.620%	$213.719	$213.72	$213.70	$213.70
Purchase #7	$104.33	13.381%	$118.2904	$118.29	$118.30	$118.30
7 purchase totals =	$952.46		$1,054.1361	$1,054.15	$1,054.20	$1,054.10