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	$200.50	9.672%	$219.8924	$219.89	$219.90	$219.90
Purchase #2	$53.81	6.114%	$57.0999	$57.10	$57.10	$57.10
Purchase #3	$42.65	4.190%	$44.437	$44.44	$44.45	$44.40
Purchase #4	$71.74	12.734%	$80.8754	$80.88	$80.90	$80.90
Purchase #5	$245.79	5.121%	$258.3769	$258.38	$258.40	$258.40
Purchase #6	$90.62	6.764%	$96.7495	$96.75	$96.75	$96.70
Purchase #7	$246.53	13.308%	$279.3382	$279.34	$279.35	$279.30
7 purchase totals =	$951.64		$1,036.7693	$1,036.78	$1,036.85	$1,036.70