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	$21.98	3.746%	$22.8034	$22.80	$22.80	$22.80
Purchase #2	$211.56	12.759%	$238.5529	$238.55	$238.55	$238.60
Purchase #3	$166.58	12.176%	$186.8628	$186.86	$186.85	$186.90
Purchase #4	$158.73	12.295%	$178.2459	$178.25	$178.25	$178.20
Purchase #5	$182.90	9.269%	$199.853	$199.85	$199.85	$199.90
Purchase #6	$91.44	7.401%	$98.2075	$98.21	$98.20	$98.20
Purchase #7	$73.34	7.523%	$78.8574	$78.86	$78.85	$78.90
7 purchase totals =	$906.53		$1,003.3829	$1,003.38	$1,003.35	$1,003.50