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	$148.64	10.466%	$164.1967	$164.20	$164.20	$164.20
Purchase #2	$156.64	13.704%	$178.1059	$178.11	$178.10	$178.10
Purchase #3	$155.49	7.817%	$167.6447	$167.64	$167.65	$167.60
Purchase #4	$106.39	13.589%	$120.8473	$120.85	$120.85	$120.80
Purchase #5	$199.89	9.423%	$218.7256	$218.73	$218.75	$218.70
Purchase #6	$86.96	5.490%	$91.7341	$91.73	$91.75	$91.70
Purchase #7	$173.82	13.272%	$196.8894	$196.89	$196.90	$196.90
7 purchase totals =	$1,027.83		$1,138.1437	$1,138.15	$1,138.20	$1,138.00