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	$59.70	5.420%	$62.9357	$62.94	$62.95	$62.90
Purchase #2	$149.86	6.491%	$159.5874	$159.59	$159.60	$159.60
Purchase #3	$137.41	9.653%	$150.6742	$150.67	$150.65	$150.70
Purchase #4	$179.82	6.464%	$191.4436	$191.44	$191.45	$191.40
Purchase #5	$239.59	3.672%	$248.3877	$248.39	$248.40	$248.40
Purchase #6	$198.31	6.405%	$211.0118	$211.01	$211.00	$211.00
Purchase #7	$53.79	3.615%	$55.7345	$55.73	$55.75	$55.70
7 purchase totals =	$1,018.48		$1,079.7749	$1,079.77	$1,079.80	$1,079.70