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	$177.67	10.371%	$196.0962	$196.10	$196.10	$196.10
Purchase #2	$163.94	6.215%	$174.1289	$174.13	$174.15	$174.10
Purchase #3	$102.50	8.793%	$111.5128	$111.51	$111.50	$111.50
Purchase #4	$30.73	5.662%	$32.4699	$32.47	$32.45	$32.50
Purchase #5	$187.69	12.817%	$211.7462	$211.75	$211.75	$211.70
Purchase #6	$222.81	3.216%	$229.9756	$229.98	$230.00	$230.00
Purchase #7	$16.64	11.506%	$18.5546	$18.55	$18.55	$18.60
7 purchase totals =	$901.98		$974.4842	$974.49	$974.50	$974.50