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	$96.69	10.804%	$107.1364	$107.14	$107.15	$107.10
Purchase #2	$39.45	7.449%	$42.3886	$42.39	$42.40	$42.40
Purchase #3	$12.64	7.342%	$13.568	$13.57	$13.55	$13.60
Purchase #4	$80.33	12.658%	$90.4982	$90.50	$90.50	$90.50
Purchase #5	$245.43	4.399%	$256.2265	$256.23	$256.25	$256.20
Purchase #6	$164.36	12.754%	$185.3225	$185.32	$185.30	$185.30
Purchase #7	$14.53	13.418%	$16.4796	$16.48	$16.50	$16.50
7 purchase totals =	$653.43		$711.6198	$711.63	$711.65	$711.60