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	$80.29	3.156%	$82.824	$82.82	$82.80	$82.80
Purchase #2	$142.94	5.553%	$150.8775	$150.88	$150.90	$150.90
Purchase #3	$183.81	4.672%	$192.3976	$192.40	$192.40	$192.40
Purchase #4	$93.49	5.400%	$98.5385	$98.54	$98.55	$98.50
Purchase #5	$125.31	5.165%	$131.7823	$131.78	$131.80	$131.80
Purchase #6	$100.93	4.264%	$105.2337	$105.23	$105.25	$105.20
Purchase #7	$33.41	12.793%	$37.6841	$37.68	$37.70	$37.70
7 purchase totals =	$760.18		$799.3377	$799.33	$799.40	$799.30