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	$26.78	7.764%	$28.8592	$28.86	$28.85	$28.90
Purchase #2	$159.57	3.211%	$164.6938	$164.69	$164.70	$164.70
Purchase #3	$181.73	3.424%	$187.9524	$187.95	$187.95	$188.00
Purchase #4	$182.72	4.691%	$191.2914	$191.29	$191.30	$191.30
Purchase #5	$218.51	5.527%	$230.587	$230.59	$230.60	$230.60
Purchase #6	$49.90	9.151%	$54.4663	$54.47	$54.45	$54.50
Purchase #7	$195.39	5.653%	$206.4354	$206.44	$206.45	$206.40
7 purchase totals =	$1,014.60		$1,064.2855	$1,064.29	$1,064.30	$1,064.40