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	$109.43	3.499%	$113.259	$113.26	$113.25	$113.30
Purchase #2	$150.25	11.719%	$167.8578	$167.86	$167.85	$167.90
Purchase #3	$38.81	10.229%	$42.7799	$42.78	$42.80	$42.80
Purchase #4	$16.78	9.279%	$18.337	$18.34	$18.35	$18.30
Purchase #5	$58.88	5.867%	$62.3345	$62.33	$62.35	$62.30
Purchase #6	$178.32	7.273%	$191.2892	$191.29	$191.30	$191.30
Purchase #7	$228.58	12.727%	$257.6714	$257.67	$257.65	$257.70
7 purchase totals =	$781.05		$853.5288	$853.53	$853.55	$853.60