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	$187.72	3.869%	$194.9829	$194.98	$195.00	$195.00
Purchase #2	$49.57	3.410%	$51.2603	$51.26	$51.25	$51.30
Purchase #3	$160.38	11.698%	$179.1413	$179.14	$179.15	$179.10
Purchase #4	$80.73	12.272%	$90.6372	$90.64	$90.65	$90.60
Purchase #5	$113.32	5.547%	$119.6059	$119.61	$119.60	$119.60
Purchase #6	$130.38	9.632%	$142.9382	$142.94	$142.95	$142.90
Purchase #7	$69.89	3.356%	$72.2355	$72.24	$72.25	$72.20
7 purchase totals =	$791.99		$850.8013	$850.81	$850.85	$850.70