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	$155.92	4.421%	$162.8132	$162.81	$162.80	$162.80
Purchase #2	$31.59	3.753%	$32.7756	$32.78	$32.80	$32.80
Purchase #3	$117.37	5.571%	$123.9087	$123.91	$123.90	$123.90
Purchase #4	$160.30	5.758%	$169.5301	$169.53	$169.55	$169.50
Purchase #5	$174.52	4.652%	$182.6387	$182.64	$182.65	$182.60
Purchase #6	$105.69	3.266%	$109.1418	$109.14	$109.15	$109.10
Purchase #7	$6.98	13.595%	$7.9289	$7.93	$7.95	$7.90
7 purchase totals =	$752.37		$788.7370	$788.74	$788.80	$788.60